Nautical, sailing and navigation terms, glossary, definitions               Skysail Training Home Page

In French - Glénans Sailing  

Complete Navigation Glossary - Navigation_acronyms_abbreviations_definitions_glossary.pdf

C   E   J   O   S   T        Abbreviations


Abaft - Toward the rear (stern) of the boat. Behind.

Abeam - At right angles to the keel of the boat, but not on the boat.

Aboard - On or within the boat.

Above Deck - On the deck (not over it - see Aloft)

Abreast - Side by side; by the side of.

Adrift - Loose, not on moorings or towline.

Advection Fog (sea fog) - Can occur any time warm, moist air blows over a surface cool enough to drop it's temperature below the dew point.

Aft - Toward the stern of the boat.

Aground - Touching or fast to the bottom.

Ahead - In a forward direction.

Aids To Navigation – (ATON) objects like buoys at sea to supplement natural landmarks, indicating safe and unsafe waters.

Alee - Away from the direction of the wind. Opposite of windward.

Aloft - Above the deck of the boat.

Amidships - In or toward the centre of the boat.

Amphidrome, amphidromic point - a point in the ocean with no tidal range. There are several round the coast of the UK.

Anchorage - A place suitable for anchoring in relation to the wind, seas and seabed

Andrew - the Royal Navy.

Angle of Vanishing Stability - AVS - the angle of heel at which a boat may recover to the vertical or just carry on capsizing.

Apparent wind - the direction of the wind relative to the boat when the boat is moving. When close to the wind, forward motion will reduce the apparent wind angle; it will also increase the apparent wind speed.

Astern - In back of the boat, opposite of ahead.

Athwartships - At right angles to the centreline of the boat; rowing boat seats are generally athwart ships.

Aweigh - The position of anchor as it is raised clear of the bottom.

Avast - Command meaning "stop what you're doing"


Back - when the wind changes direction anti clockwise

Backstay - A wire support for the mast, usually running from the stern to the head of the mast.

Baggywrinkle - Clumps of frayed rope that protect the sails from chafing against the lines.

Ballast - weights, usually metal, placed low in a boat to provide stability.

Barber Hauler - A line attached to the jib or jib sheet, used to adjust the angle of sheeting by pulling the sheet toward the centreline of the boat.

Batten Down - Secure hatches and loose objects both within the hull and on deck.

Batten - Flexible strip of wood or plastic, most commonly used horizontally in the mainsail to support the aft portion, or leech, so that it will not curl.  Fully battened - the battens extend from the luff to the leach of the mainsail. This gives a more powerful sail shape.

Beam - The maximum width of the boat.

Bearing - The direction of an object expressed either as a true bearing as shown on the chart, or as a bearing relative to the heading of the boat. A Relative bearing is measured from the heading of the boat,

Beat - to sail as close to the wind as possible.

Belay - To temporarily secure a line to a cleat. Or as a command "disregard the last order"

Below - Beneath the deck.

Bend - a knot used to attach two ropes.

Bermuda rig - a sloop with fore and aft sails with no gaff.  Sometimes called a masthead rig.

Berth – a sleeping area; where a ship is moored.

Bight - The part of the rope or line, between the end and the standing part, on which a knot is formed.

Bilge - A rounding of the hull along the length of the boat where the bottom meets the side.

Bilgeboards - are on either side of the centreline at the bilges. Similar to centreboards, and used to minimise lee way.

Bilge keel - two keels either side of the centreline of the hull, enabling the boat to stand upright when aground.

Binnacle - A pillar for the compass, raising it to a convenient position.

Bitter end - The last part of a rope or chain. The inboard end of the anchor rode (line)

Block - a pulley

Boat - A fairly indefinite term. A craft smaller than a ship. One definition is a small craft carried aboard a ship. Submarines are known as boats.

Boat Hook - A short shaft with a fitting at one end shaped to facilitate use in putting a line over a piling, recovering an object dropped overboard, or in pushing or fending off.

Bobstay - Wire Stay underneath the bowsprit; helps to counteract the upward pull exerted by the forestay.

Boom Crutch - Support for the boom, holding it up and out of the way when the boat is anchored or moored. Unlike a gallows frame, a crutch is stowed when the boat is sailing.

Boom - free swinging spar attached to the foot of the sail with forward end pivoting on the mast.

Boom Crutch - Support for the boom, holding it up and out of the way when the boat is anchored or moored.

Bumpkin - Short spar extending aft from the transom. Used to anchor the backstay or the sheets from the mizzen on a yawl or ketch.

Boot top - A painted stripe that indicates the waterline.

Bottlescrew - an adjustable screw device to tension a shroud or other wire.

Bow - The forward part of a boat.

Bowline - Knot used to form a loop in a line

Bow Line - A dock line leading from the bow to the pontoon.

Bowsprit - A short spar extending forward from the bow. Normally used to anchor the forestay.

Brail - Partially furling sails to lessen wind resistance. On a square sail this is accomplished with leech and clew lines. See "Scandalize".

Bridge - The location from which a vessel is steered and its speed controlled.

Bridge Deck - The partition between the cockpit and the cabin.

Bridle - A short length of wire with a line attached at the midpoint. A bridle is used to distribute the load of the attached line. Often used as boom travellers and for spinnaker down hauls

Brightwork - Varnished woodwork and/or polished metal.

Broach – to round up into the wind, usually unplanned due to sudden pressure of wind!

Brow - the shore end of a pontoon

Bulkhead - An interior partition commonly used to stiffen the hull. May be watertight.

Bullseye - A round eye through which a line is led, usually in order to change the direction of pull.

Bulwark - A vertical ‘side wall’ above deck level designed to keep water out of, and sailors in the boat.

Bunk - Sleeping berth

Buoy - An anchored float used for marking a position on the water or a hazard or a shoal and for mooring.

Burdened Vessel - That vessel which, according to the applicable Navigation Rules, must give way to the privileged vessel. The term has been superseded by the term "give-way".

Burgee – small triangular flag of a club or organisation. Usually flown at the crosstrees.

By the lee - to sail by the lee is to sail downwind with the wind coming from the same side as the mainsail.  A gybe is then imminent and great care must be taken.


Cabin - A compartment for passengers or crew.

Capsize - To turn over.

Capstan - drum like part of the windlass used for winding in rope, cables, or chain connected to cargo or anchors

Cardinal Points - The compass points of North, East, South and West. Cardinal marks are placed N E S W of the danger they mark.

Cast Off - To let go.

Catamaran - A twin-hulled boat, with hulls side by side.

Catenary - The curve (sag) of a rope, cable or chain hung between two points such as the anchor rode or towing line.

Centre of Effort - an imaginary point on the sail where the force of wind is concentrated

Centre of Gravity - an imaginary point in the boat where the weight is centered

Centre of Lateral Resistance - an imaginary point where the boat will rotate about its keel 

Centre board - A board lowered through a slot in the centreline of he hull to reduce sideways skidding or leeway. Unlike a daggerboard, which lifts vertically, a centre board pivots around a pin, usually located in the forward top corner, and swings up and aft.

Chafing gear – Tubing, leather or cloth wrapping used to protect a line from chafing on a rough surface.

Chain plate - The fitting used to attach shrouds to the hull.

Chart - A map for use by navigators.

Chart datum - horizontal datum from which charted depths, drying heights and height of tide are referred.

Chine - The intersection of the bottom and sides of a flat or v-bottomed boat.

Chine - A line, running along the length of the boat, where the bottom of the hull forms an angle to the side. Not found on round-bottom boats.

Cleat - A fitting to which lines are made fast. The classic cleat to which lines are belayed is approximately anvil-shaped.

Clew - For a triangular sail, the aft corner.

Close reach - the point of sailing between a beam reach and a beat

Clove Hitch - A knot for temporarily fastening a line to a spar or piling.

Clutter - unwanted radar echoes usually caused by waves (se clutter) or rain.

Coach Roof - Also trunk. The cabin roof, raised above the deck to provide headroom in the cabin.

Coaming - A vertical extension above the deck to prevent water from entering the cockpit. May be broadened to provide a base for winches.

Cockpit - An opening in the deck from which the boat is handled.

Coil - To lay a line down or make a coil in circular turns.

Colregs - International Rules for Preventing Collisions at Sea.  Rules of the Road.

Companionway - The main entrance to the cabin, usually including the steps or ladder down into the cabin.

Counter - At the stern of the boat, that portion of the hull emerging from below the water, and extending to the transom. Apt to be long in older designs, and short in more recent boats.

Coriolis force - is the effect of the Earth's rotation on the direction of the wind.  In the Northern hemisphere wind is deflected to the right. At sea level, friction affects the wind also in speed and direction.

Course - The direction in which a boat is steered. The actual track of the boat.

Coxswain - Sailor in charge of and steering a small boat

Crosstrees - Horizontal members attached to the mast acting as spreaders for the shrouds

Cruising chute -  a light nylon fore sail like a large genoa, attached only at tack and head, with a sheet to the stern of the boat.

Cuddy - A small sheltered cabin in a boat.

Cunningham - A mainsail control device, using a line to pull down the mainsail a short distance from the luff to the tack. Flattens the sail.

Named for Briggs Cunningham, US sailor.

Current - The horizontal movement of water.

Cutter - a single masted boat with two foresails and one mainsail


Daggerboard - A board dropped vertically through the hull to prevent leeway. May be completely removed for beaching or raised for sailing downwind. It cannot lift like a centreboard.

Dan buoy - Buoyant weighted pole with flag and light, thrown overboard to mark the position of a Man Overboard (MOB)

Davits - Small cranes used to raise or lower small boats and light items from deck to water level.

Day mark - a beacon, usually on land, to convey pilotage information

Dead Ahead - Directly ahead.

Dead Astern - Directly aft.

Dead-Eyes - Blocks in the shroud rigging used to adjust tension

Deadlight - Either a cover clamped over a porthole to protect it in heavy weather or a fixed light set into the deck or cabin roof to provide light below.

Dead Reckoning - also Ded Reckoning or DR. Sometimes believed to be an abbreviation of Deduced Reckoning. A boat’s position derived without considering the effect of tide

Deck - A permanent covering over a compartment, hull or any part thereof.

Deviation - the effect in degrees of the boat itself on the bearing of a magnetic compass. It may vary with the heading of the boat.

Dinghy - A small open boat. A dinghy is often used as a tender for a larger craft.

Direction of buoyage - the direction of the rising tide, into harbour. Used to indicate the position of lateral (Port and Starboard hand) marks. Shown by a broad magenta arrow on charts.

Displacement - The weight of water displaced by a floating vessel, thus, a boat's weight.

Displacement Hull - A type of hull that ploughs through the water, displacing a weight of water equal to its own weight, even when more power is added.

Ditty Bag - Small bag used for carrying and stowing small personal items or kits

Dock - A protected water area in which vessels are moored. The term is often used to denote a pier or a wharf.

Dolphin - A group of piles driven close together and bound into a single structure.

Dodger - A screen, usually canvas, around  the cockpit to protect crew from spray and wind.

Downhaul - A line used to pull a spar, such as the spinnaker pole, or a sail, particularly the mainsail, down.

Draught - The depth of water of a boat’s keel below sea level

Drogue - a small parachute used as a sea anchor to reduce drift downwind

Drift - to float freely. Also the distance travelled by the tide in one hour.


Ebb - A falling tide.

Ensign – national maritime flag, usually flown at the stern.


Fairlead - A fitting used to alter the direction of a line, such as a turning block

Fathom - Six feet.

Fender - A cushion, placed between boats, or between a boat and a pier, to prevent damage.

Fetch – the uninterrupted distance over which the wind blows.  Also sail to a mark without needing to change course.

Fid - Tool used by riggers in splicing a line.

Fiddle - a raised edge on a table to stop eg plates falling off.

Figure Eight Knot - A knot in the form of a figure eight, placed in the end of a line to prevent the line from passing through a grommet or a block.

Fin Keel - a single keeled boat

Flare - The outward curve of a vessel's sides near the bow. Or a distress signal.

Flood - A rising tide.

Flubber - the rubber dinghy.

Fluke - The 'hook' of an anchor.

Fo'c'sle - abbreviation of forecastle. Refers to that portion of the cabin which is farthest forward. In square-riggers often used as quarters for the crew.

Fog - visibility of less than 1,000 metres.

Following sea - An overtaking sea that comes from astern.

Foot - For a triangular sail, the bottom edge.

Fore And Aft - In a line parallel to the keel.

Foremast - vertical spar most forward

Forepeak - The compartment farthest forward in the bow of the boat. Often used for anchor or sail stowage. In larger ships the crews’ quarters

Forestay - Wire, sometimes rod, support for the mast, running from the bowsprit or foredeck to a point at or near the top of the mast.

Foretriangle - the triangle formed by the forestay, mast, and fore deck.

Forward or for'd - Toward the bow of the boat.

Fouled - Any piece of equipment that is jammed or entangled.

Fractional Rig - A mast in which the forestay does not go to the very top of the mast, but instead to a point 3/4~ 7/8's, etc., of the way up the mast. this helsp to control the bend of the mast. It may need running backstays.

Frames - Ribs that form the shape of the hull

Free - the wind frees when it allows you to sail closer to your destination.

Freeboard - The distance between the deck and the waterline. Most often it will vary along the length of the boat. (see: Shear)


Gaff - a free swinging spar attached to the top edge of a sail

Galley - The kitchen area of a boat.

Gangway - The area of a ship's side where people board and disembark.

Garboard - Used in conjunction with strake. Refers to the planks, or strakes, on either side of and adjacent to the keel.

Gate - an area where tidal streams may help or prevent a vessel from making a passage through it.

Genoa - a large foresail which overlaps behind the mast.

George - the automatic steering. Autohelm.

Geostrophic wind - is the wind that would result from an exact balance between the Coriolis force and the pressure gradient force.

Give-Way Vessel -  the vessel which must alter course and/or speed in meeting, crossing, or overtaking situation which is a potential collision.

Gooseneck - The fitting that connects the boom to the mast.

Goosewing - to sail downwind with the mainsail and genoa on opposite sides of the boat to maximise the exposed sail area. Otherwise the genoa is blanketed by the mainsail. Usually only possible in calm seas. Also known as 'wing and wing'.

GPS - Global Positioning System

Grab Rails - Hand-hold fittings mounted on cabin tops and sides for personal safety when moving around the boat.

Ground Tackle - A collective term for the anchor and its associated gear.

Gunter Rig - Similar to a gaff rig, except that the spar forming the "gaff" is hoisted to an almost vertical position, extending well above the mast.

Gunwale - Most generally, the upper edge of the side of a boat. Pronounced gun'l.

Guy - A line used to control the end of a spar. A spinnaker pole, for example, has one end attached to the mast, while the free end is moved back and forth with a guy.


Halyards - Lines used to hoist or lower sails or flags.

Halyards - lines used to haul up the sail and the wooden spars (boom and gaff) that hold the sails in place.

Hard Chine - A sharp corner between the hull side and the hull bottom of a boat so constructed.

Hatch - an opening in the deck for entering below.

Head - For a triangular sail, the top corner. Also a marine toilet.

Headfoil - a grooved rod fitted over the forestay to provide support for luff of the sail.

Heading - The direction in which a vessel's bow points at any given time.

Headsails - Any sail forward of the foremast.

Headway - Forward motion of boat opposite to sternway

Heave to - to stop a boat with the sails on opposite sides so it only drifts sideways  (past tense hove to)

Helm - The wheel or tiller controlling the rudder.

Helmsman - Sailor who steers the boat.

Hitch - A knot used to secure a rope to another object or to another rope.

Hold - A compartment below deck in a vessel, used solely for carrying cargo.

Hull - The main body of a vessel.


Inboard - More toward the centre of a vessel; inside; an engine fitted inside a boat.

Iron topsail (top'sl_ - the engine

Isobar - a line of equal pressure on a synoptic chart. Close isobars indicate strong winds.


Jacobs Ladder - A rope ladder, lowered from the deck, as when pilots or passengers come aboard.

Jackstay - A line of webbing or wire running along the deck. Used to attach a safety harness to prevent crew falling overboard.

Jetty - A structure projecting out from the shore; a jetty may protect a harbour entrance.

Jettison - To throw overboard.

Jib - A triangular foresail in front of the foremast.

Jury rig - a temporary rig constructed  rig to allow you to continue sailing after the mast or part of it has broken


Keel – the heavy vertical fin below a boat, which provides stability and reduces leeway. Also the lowest fore and aft timber in a ship.

Ketch - a type of 2 masted rig where the mizzen sail is smaller than the mainsail

Kicking strap, kicker - A system used to hold the boom down, particularly when boat is sailing downwind, so that the mainsail area facing the wind is kept to a maximum. Also flattens the mainsail when sailing upwind. Frequently extends from the boom to a location near the base of the mast. Usually tackle or lever-operated.   Also known as a vang.

Knockdown - what it says, the boat is laid flat by wind or waves

Knot - A measure of speed equal to one nautical mile (1852 metres) per hour.

Knot - A fastening made by tying rope to form a stopper, to enclose or bind an object, to form a loop or a noose, to tie a small rope to an object, or to tie the ends of two small ropes together.


Lateral - to the side; term used for port and starboard hand marks

Latitude - The distance north or south of the equator measured and expressed in degrees, minutes and decimal minutes (or seconds). Lines of latitude are termed parallels

Lay - to sail to a mark without needing to change course or lose speed (same as fetch)

Lazarette - A storage space in a boat's stern area.

Lazy Jack - Light lines from the mast to the boom, forming a cradle into which the mainsail may be lowered.

Lead - Refers to the direction in which a line goes. A boom vang, for example, may "lead to the cockpit."

Lead - a weight with a marked line to measure depth.  Traditionally with a cup in the bottom containing tallow to recover, sand, shells, mud etc and determine the nature of the seabed.

Lee helm - when the boat wants to steer away from the wind and the helm has to counteract it with the rudder. This is dangerous as the boat will gybe if not controlled.

Leech - The aft edge of a triangular sail.

Leech Line - A line running through the leech of the sail, used to tighten it.

Lee - The side sheltered from the wind.  Downwind.

Leeward - The direction away from the wind. Opposite of windward. Sometimes pronounced loo'ard.

Leeway - The sideways movement of the boat caused by the wind or current.

Lee Boards - Pivoting boards on either side of a boat which serve the same function as a centreboard.

Lee bow - to sail with the tide under the lee bow so the boat is pushed to windward.

Lines - Rope or cordage used for various purposes aboard a boat.

Log (book) - A record of events, distance run and courses on a boat. Also, a device to measure speed.

Length overall (LOA) - total length of a boat

Length (waterline) (LWL) - length of boat at the waterline.

Longitude - The distance in degrees east or west of the meridian at Greenwich

Loose-Footed - Describes a mainsail attached to the boom at the tack and clew, but not along the length of its foot.

Lubber Line - A mark or permanent line on a compass indicating the direction forward parallel to the keel when properly installed

Luff - The forward edge of a triangular sail. In a mainsail the luff is that portion that is closest to the mast.

Luff or Luffing - To steer the boat into the wind. When the vessel is brought too far into the wind the forward end or luff of the sails begin to shiver or shake.


Make fast – to attach.

Making way - being propelled through the water

Mainmast - the tallest mast of the ship; on a schooner, the mast furthest aft.

Mainsail - The lowest square sail on the mainmast.

Marline - A light line which has been tarred.

Marlinspike - a spike used by sailors when splicing lines.

Mast - Main vertical spar used to support sails and their running rigging and in turn supported by standing rigging

Mast Step - Fitting or construction into which the base of the mast is placed.

Masthead Rig - A design in which the forestay runs to the peak of the mast.

Meridian - a line of longitude.

Midships - Approximately in the location equally distant from the bow and stern.

Mizzen - the aftmost mast.

Mizzen - A fore and aft sail flown on the mizzenmast.

MOB - Man Over Board

Mooring - An arrangement for securing a boat to a mooring buoy or a pier.

Multihull - a boat with more than one hull (a catamaran or trimaran for instance)


Nautical Mile - One minute of latitude; approximately 6076 feet - about 1/8 longer than the statute mile of 5280 feet.

Navigation - The art and science of conducting a boat safely from one point to another.

Neap - when the rise and fall of the tide is at a minimum (half moon)

No-go zone - a point of sailing at which the boat will no longer make progress into the wind 


Oar - Device used to propel small boats by rowing

Offshore - when sailing a long distance from the shoreline

Offshore wind - when the wind is blowing away from the shoreline

Off the wind, offwind - to sail away from the wind. Not beating.

Onshore wind - as wind blowing towards thye shore

Outhaul - a line used to control the tension at the foot of the mainsail

Overstand - to stay too long on one tack 

Outboard - Toward or beyond the boat's sides. A detachable engine mounted on a boat's stern.

Outhaul - Usually a line or tackle, an outhaul is used to pull the clew of the mainsail towards the end of the boom, thus tightening the foot of the sail.

Overhaul - Straightening out misaligned or partially fouled sails and rigging

Overboard - Over the side or out of the boat.

Overfalls - rough water caused by strong tide over a rough shallow seabed


Painter - a rope at the front of a small boat to tie the boat i.e. to a pontoon

Pay Out: - to feed line over the side of the boat, hand over hand.

Perch - a pole to mark a channel in a river

Pier - A loading platform extending at an angle from the shore.

Pile - A wood, metal or concrete pole driven into the bottom. Craft may be made fast to a pile; it may be used to support a pier (see PILING) or a float.

Piling - Support post for wharves, piers etc.; constructed of piles (see PILE)

Pilothouse - a small cabin on the deck of the ship that protects the steering wheel and the crewman steering.

Pinch - to point a boat so high into the wind that the sails lose power (like 'luff')

Pitchpole - to be capsized; the boat somersaults bow first.

Planking - wood boards that cover the frames outside the hull.

Piloting - Navigation by use of visible references, the depth of the water, etc.

Planing - A boat is said to be planing when it is essentially moving over the top of the water rather than through the water.

Planing Hull - A type of hull shaped to skim easily across the water at high speed.

Point (compass) - Eleven and a quarter degrees. The compass was traditionally divided into 32 divisions of the 360º card.

Points of sailing - the various angles that the boat sails on relative to the apparent wind

Pompey - Portsmouth

Pooped - overtaken by a wave.

Port - The left side of a boat looking forward. A harbour.

Pulpit - A metal framework on deck at the bow or stern. Provides a safety railing.

Pushpit - as above, located on the stern. Used to mount aerials, life buoys, dan buoys, liferafts, fenders, etc, etc!


Quarter - The sides of a boat aft of amidships.

Quartering Sea - Sea coming on a boat's quarter.


Race or tide race - a very strong tidal flow, often very rough

RACON - Radar Beacon

Radiation Fog - Fog over land caused by land radiating heat into a clear sky, thus cooling the air to dew point and condensation of water vapour into fog.

Rake - The fore or aft angle of the mast. Can be deliberately induced (by adjustment of the standing rigging) to flatten sails, balance steering, etc. Normally a mast is raked slightly aft.

Reach – to sail with the wind on the beam (side of the boat). Also a clear channel of water.

Ready about - a call made by the helm to prepare the crew for  a tack or gybe. When the crew say 'ready', the helm calls 'Lee oh' before making the tack.

Reef - to reduce the area of a sail. 

Reef  Knot - A knot used to join two lines of similar size.  Not reliable for regular use.

Reef points - A horizontal line of light lines on a sail which may be tied to the boom, reducing the area of the sail during heavy winds.

Reeve - to thread a line through an eye,  fairlead or block.

Rigging: - the lines that hold up the masts and move the sails (standing and running rigging).

Roach - The curved portion of a sail extending past a straight line drawn between two corners. In a mainsail, the roach extends past the line of the leech between

the head and the clew and is often supported by battens.

Rocker - The upward curvature of the keel towards the bow and stern.

Rode - The anchor line and/or chain.

Rope - In general, cordage as it is purchased at the chandler. When it comes aboard a vessel and is put to use it becomes line.

Roller reefing - Reduces the area of a sail by rolling it around a stay, the mast, or the boom. Most common on headsails.

Rubbing rail - Also rubbing strake. An applied or thickened member at the rail, running the length of the boat; serves to protect the hull when alongside a pontoon or another boat.

Rudder - A vertical plate or board for steering a boat.

Run – To sail downwind. To allow a line to feed freely.

Running Backstay: Also runner, or preventive backstay. A stay that supports the mast from aft, usually from the quarter rather than the stern. When the boat is sailing downwind, the runner on the leeward side of the mainsail must be released so as not to interfere with the sail. On tacking, the leeward backstay may be released and windward one is tightened.

Running rigging -The adjustable rigging such as sheets used to control sails and sail control equipment.

Running Lights - Lights required to be shown on boats underway at night.


Sail - a piece of cloth that catches or directs the wind and so powers a vessel.

Sailing Rig - the equipment used to sail a boat, including sails, booms and gaffs, lines and blocks.

Scandalize - On a gaff rig the sail is made loose footed, the clew is brought forward along the boom and the sailcloth is drawn up in folds along the gaff and mast. From this position the sail is instantly available for use, but does not catch the wind.. On a Bermuda rig you can raise the boom very high to achieve a similar effect

Schooner - Sailing ships with at least 2 masts (foremast and mainmast) with the mainmast being the taller.

Scope - Technically, the ratio of length of anchor rode in use to the vertical distance from the bow of the vessel to the bottom of the water. Usually five to one.

Significant wave height - the mean height of the highest one third of the waves, which approximately corresponds to the wave height estimated by an experienced observer. Some waves will be double this height.

for calm weather and more scope in storm conditions.

Screw - A boat's propeller.

Scupper - Drain in cockpit, coaming, or toe-rail allowing water to drain out and overboard. When in toe rail, properly known as "freeing port"

Scuttle- A round window in the side or deck of a boat that may be opened to admit light and air, and closed tightly when required.

Seabreeze - a thermal wind which blows onshore, usually in summer.

Seat Locker - A storage locker located under a cockpit seat.

Seacock - A through hull valve, a shut off on a plumbing or drain pipe between the vessel's interior and the sea.

Seat locker - A storage locker located under a cockpit seat.

Self-bailing cockpit - A watertight cockpit with scuppers, drains, or bailers that remove water.

Self-tacking - Normally applied to a sail that requires no adjustment when boat is tacked. Normally applied to a jib sail.

Seamanship - All the arts and skills of boat handling, ranging from maintenance and repairs to piloting, sail handling, marlinespike work, and rigging.

Sea Room - A safe distance from the shore or other hazards.

Seaworthy - A boat or a boat's gear able to meet the usual sea conditions.

Secondary port - a port with no local tide tables for time and height of high and low tide.  Secondary port differences enable you to calculate times and heights based on the Standard Port.

Secure - To make fast.

Set - Direction toward which the current is flowing.

Sheer - The line of the upper deck when viewed from the side. Normal sheer curves up towards the bow and stern,

Reverse sheer curves down towards the bow and stern. Compound sheer, curving up at the front of the boat and down at the stern, and straight sheer are uncommon.

Sheer Strake - The topmost planking in the sides, often thicker than other planking.

Sheets - Lines used to control the position of a sail.

Shrouds - Lateral supports for the mast, usually of wire or metal rod.

Ship - A larger vessel usually thought of as being used for ocean travel. A vessel able to carry a "boat" on board.

Shroud: - a line or wire running from the top of the mast to the spreaders, then attaching to the side of the vessel.

Skeg: For sailboats, usually refers to a structural support to which the rudder is fastened.

Slab Reefing - Also points reefing, and sometimes jiffy reefing. Reduces the area of the mainsail by partially lowering the sail and resecuring the new foot by tying

it to the boom with points, or light lines attached to the sail.

Slack - Not fastened; loose. Also, to loosen.

Slamming - when the forward part of the hull 'slams' into the waves when beating to windward.

Sloop - a Bermuda rig boat with one foresail, and mainsail.

Slot - the gap between foresail and mainsail.

Snub - To stop the running out of a line by taking a half turn around a cleat, piling, eg to gradually stop a boat coming alongside.; to suddenly stop or secure a line.

Snubber - and elastic line used to reduce snatch in an anchor rode or mooring line.

Sole - The floor of the cockpit or cabin.

Sounding - A measurement of the depth of water.

Spar - a pole or a beam.

Spinnaker - A large, light, symmetrical triangular sail, flown from the mast in front of all other sails and the forestay. Used for sailing downwind or on a reach. Supported by a spinnaker pole.

Spreaders - Also crosstrees. Horizontal struts extending from the mast, giving a better angle for the shrouds to stiffen the mast.

Springs - when the rise and fall of the tide is at a maximum (Full or new moon)

Spring Line - A line used in docking, undocking, or to prevent the boat from moving forward or astern while made fast to a dock.

Standing rigging - Permanent rigging used to support the spars. May be adjusted during sailing, particularly racing.

Stay - a line or wire from the mast to the bow or stern of a ship, for support of the mast (fore, back, running, and triatic stays).

Staysail - A sail that is set on a stay, and not on a yard or a mast.

Stem - the  very front of the bow.

Strake - On wooden boats, a line of planking running from the bow to the stern along the hull.

Squall - A sudden, violent wind often accompanied by rain.

Stanchion - Vertical poles on the gunwhales to support safety lines

Standard Port - a port with tide tables and a tidal curve in the almanac.

Standing Part - The part of a line which is made fast. The main part of a line as distinguished from the bight and the end.

Stand on Vessel - The vessel which should hold its course and speed during a meeting, crossing, or overtaking situation which is a potential collision.

Starboard - The right side of a boat when looking forward.

Stay - a supporting line, usually wire, eg forestay, backstay

Stem - The most forward vertical structural member in the bow.

Stern - The after part of the boat.

Stern board - make a stern board - to sail backwards.

Stern Line - A docking line leading from the stern.

STIX - Stability Index: a composite index of stability factors to give a single measure of boat stability. Supposedly more meaningful than Angle of Vanishing Stability

Storm jib - a small foresail,of tough cloth for use in a storm.

Stow - To put an item in its proper place.

Strake: On wooden boats, a line of planking running from the bow to the stern along the hull.

Swamp - To fill with water, but not settle to the bottom.

Sweat - Sweat is the act of hauling a halyard to raise a sail or spar done by pulling the slack outward and then downward. Tail is controlling, coiling, and securing the running end of the halyard.

Swell - the dominant wave pattern, often long wavelength and high, having travelled long distances and not due to local weather conditions.

Synoptic chart - A weather chart with isobars, reflecting the state of the atmosphere over a large area at a given moment.


Tabernacle - A hinged mast step located on deck. Since it is hinged, the mast may be lowered easily.

Tackle – an arrangement of ropes and blocks to exert more tension than a single rope.

Tack - On a triangular sail, the bottom forward corner. Also, to turn the bow of the boat through the wind so the wind exerts pressure on the opposite side of the sail.  Also to sail a zig zag course into the wind.

Taffrail - The rail at the stern of the boat.

Tang - A fitting, often of sheet metal, used to attach standing rigging to a spar, or to the hull.

Tell tale - small ribbons attached just behind the luff of a sail, or on the leech, to indicate smooth airflow when the sail is trimmed correctly.

Thwart - A transverse structural member in the cockpit. In small boats, often used as a seat.

Thwartships - At right angles to the centreline of the boat.

Tide - The periodic rise and fall of water level in the oceans, and the accompanying tidal streams.

Tide gate - an area where tidal streams may help or prevent a vessel from making a passage through it.

Tiddly - tidy, shipshape.

Tiller - A bar or handle for turning a boat's rudder or an outboard motor.

Toe-rail - A low rail, often slotted, along the side of the boat. Slots allow drainage and the attachment of blocks.

Topmast - a second vertical spar carried at the top of the fore or main mast, used to fly more sail (topsail)

Topping lift - A line or wire rope used to support the boom when a boat is anchored or moored, or being reefed.

Topsides - The sides of a vessel between the waterline and the deck; sometimes referring to onto or above the deck.

Trampoline - The fabric support that serves for searing between the hulls of a catamaran.

Transit - the line through two marks or lights, or two  natural features.

Transom - The flat, or sometimes curved terminating structure of the hull at the stern of a boat.

Transponder - radar transmitter which is activated by receiving a radar echo.

Trapeze - Wire gear enabling a crew member to place all of his weight outboard of the hull, thus helping to keep the boat level.

Traveller - A fitting across the boat to which a mainsail sheet is led. The traveller may be adjusted from side to side so that the angle of the sheet can be changed to suit conditions.

Triatic stay - stay which connects the tops of mainmast and mizzen mast .

Trim - Fore and aft balance of a boat. Also, to set a sail correctly.

Trimaran - a boat with three hulls.

Trysail - a small mainsail of tough cloth for use in a storm. Usually set without the boom.


Underway - Vessel not moored, or aground, or at anchor.


Vang - A device, usually with mechanical advantage, used to pull the boom down, flattening the main sail. See Kicking Strap.

Variation - at any point on the Earth's surface, the angle between the bearing of the True North pole and the Magnetic North pole.

Veer - when the wind changes direction clockwise

Ventilator - Construction designed to lead air below decks. May have a cowl, which can be angled into or away from the wind; and may be constructed with baffles, so that water is not allowed below, as in a Dorade ventilator.

V bottom - A hull with the bottom section in the shape of a "V".


Wake - Moving waves, track or path that a boat leaves behind it, when moving across the water.

Warp - Heavier lines (rope or wire) used for mooring, anchoring and towing. May also be used to indicate moving (warping) a boat into position by pulling on a warp.

Waterline - A line painted on a hull which shows the point to which a boat sinks when it is properly trimmed (see Boot top).

Way - Movement of a vessel through the water such as headway, sternway or leeway.

Waypoint - a position defined on a chart or GPS, usually as a destination, a point on a route or reference point.

Weather helm - when the boat wants to steer towards the wind and the helm has to counteract it with the rudder. This causes drag and is usually due to the boat heeling,  and the hull becoming unsymmetrical in the water.

Weigh - to raise the anchor.

Wheel - device used for steering a boat.

Whisker Pole - A short spar, normally kept stowed, which may be used to push the clew of a jib away from the boat when the boat is running downwind.

Window - A transparent portion of a jib or mainsail.

Windward - Toward the direction from which the wind is coming. Upwind.

Wishbone - A boom composed of two separate curved pieces, one on either side of the sail. (Like a windsurfer). With this rig, sails are usually self tending and loose-footed. also 'wishbone rig'.

Withy - a pole, usually a branch of a tree to mark a channel in a river


Yacht - A pleasure vessel, a pleasure boat.

Yankee - a fore-sail flying above and forward of the jib, usually seen on bowsprit vessels.

Yaw - To swing or steer off course, as when running with a quartering sea.

Yawl Rig: two masts, aft one is smaller (shorter) and located astern of rudder post. Can be used to provide steerage-way when not under sail


Navigation Abbreviations

ATON Aid to Navigation

B Black

Bn Beacon

BTW -     Bearing to Waypoint

Bu Blue

ca -    Cable (one tenth of a Nautical Mile)

c Coarse

C Compass

Cb Cobbles

CD -        Chart Datum

CEVNI -     Code Européen des Voies de la Navigation Intérieur (European Inland Waterways regulations)

COG -     Course Over Ground

CTS -      Course To Steer

Cy Clay

Dir Directional

DR -         Dead Reckoning

DTW -      Distance To Waypoint

E East

ECM East Cardinal Mark

ED European Datum

EP -         Estimated Position

EPIRB - Emergency Position Indicating Radio Beacon

ETA -        Estimated Time of Arrival

f Fine

F Fixed

Fl Flashing

G Gravel

G Green

GPS -     Global Positioning System

HAT -       Highest Astronomical Tide

IALA International Association Of Lighthouse Authorities  (IALA A = Europe, Asia, IALA B = Americas)

Iso Isophase

IRPCS -   International Rules for Preventing Collisions at Sea

IPTS  -   International Port Traffic Signals

Kn Knot

Lat  -  Latitude

LAT -    Lowest Astronomical Tide

Long -  Longitude

Ldg Leading
Long Longitude

M -           Nautical Mile (1 minute of Latitude)
M Magnetic

M Mud

m -           metre

mb -         millibar

MHWN - Mean High Water Neaps

MHWS - Mean High Water Springs

MLWN - Mean Low Water Neaps

MLWS - Mean Low Water Springs

Mo Morse

N North

NCM North Cardinal Mark

Np -         Neap

Oc Occulting

ODAS Oceanographic Data Acquisition System

OSGB - Ordnance Survey of Great Britain (GPS datum)

PA Position Approximate

Pb Pebble

PHM Port Hand Mark

Q Quick

R Red

RACON - Radar Beacon

s Second

S South, Sand

SART Search and Rescue Radar Transponder

Sh Shel

SHM Starboard Hand Mark

SOLAS - Safety of Life at Sea Convention

SOG -     Speed Over Ground

Sp -        Spring

SW -    South West

TTG -      Time To Go

TSS - Traffic Separation Scheme

T -   True

UTC -      Universal Time Coordinated (GMT or Z - Zulu time)

VMG  -     Velocity Made Good

VQ -     Very Quick

W -     White, West

Wk -    Wreck

WGS 84 - World Geodetic System 84 - a position datum for charts and GPS receivers

XTE -       Cross Track Error

Y -         Yellow

Z -         Zulu  (Time) Military and Coastguard term for UT

º                Degree
´                 Minute
º C -         Compass Course
º M -         Magnetic Course or Bearing
º T -         True Course or Bearing

Zulu - Military and Coastguard term for UT

Radar Abbreviations 

ARPA - Automatic Radar Plotting Aid
CPA - Closest Point of Approach
Contact - Target on a radar screen (blob)
EBL - Electronic Bearing Line
Echo - Return from a target
FTC - Fast Time Constant (Rain Clutter)
MARPA - Mini Automatic Radar Plotting Aid
PRF - Pulse Repetition Frequency
Racon - Radar Beacon
RCS - Radar Cross Section
RTE -  Radar Target Enhancer
S-Band - 3 GHz band - Yacht radar
SART - Search and Rescue Transponder
STC - Sensitivity Time Control (Sea Clutter)
Target - Object which returns an echo
TCPA - Time to Closest Point of Approach
VRM - Variable Range Marker
X-Band - 9.4GHz band - Ship radar

Posted 5th March 2010