Nautical Glossary

At right angles to the vessel's centerline — directly to the side. 'Lighthouse abeam' means it is 90° to your course.

At or near the middle of the vessel. Used for helm instructions: 'hard a-midships' means centre the rudder.

Behind the vessel, or in a direction toward the stern. 'Full astern' means reversing completely.

Positioned behind the mooring buoy, connected by a warp.

A wind shifting in an anticlockwise direction (e.g., NW → W → SW). Often but not always indicates deteriorating weather.

A wire or rope running from the masthead to the stern, preventing the mast from falling forward. Split backstays allow mainsail leech tension control.

Instrument measuring atmospheric pressure. Falling pressure generally indicates worsening weather; rising indicates improvement.

The width of the vessel at its widest point. Also used directionally: 'wind abeam' means from the side.

The compass direction from your position to an object. A constant bearing indicates risk of collision.

Sailing as close to the wind as possible, usually at 40–45° apparent. Requires tacking (zigzagging) to windward.

A scale from 0 (calm) to 12 (hurricane) classifying wind strength by observed sea conditions.

The horizontal spar at the foot of the mainsail. It swings with the sail when tacking or gybing.

The forward end of the vessel.

A point of sail where the wind comes from behind the beam, roughly 135–160° from the bow. Fast and comfortable.

Abbreviation for 'by estimate' — a course estimated from a known starting point.

Wear caused by friction — rope against rope, hull, or fittings. Prevent with chafe guards and regular inspection.

The reference level to which charted depths and tide heights are compared (usually lowest astronomical tide).

A fitting with two horns for securing lines, used with a cleat hitch.

The recessed area in the deck where the crew sits and where the boat is steered.

Course Over Ground — the actual path of the vessel over the seabed, accounting for current and leeway.

A line used to apply downward tension on the mainsail's luff, moving draft forward for stronger winds. Named after Briggs Cunningham.

Estimating position by advancing a known position by course and distance travelled, without external fixes.

Dead Reckoning — position estimated from course, speed, and time without external references.

The depth of the vessel's hull below the waterline, determining the minimum water depth required.

Emergency Position Indicating Radio Beacon — a distress beacon that transmits your position to search and rescue satellites.

Being able to reach a destination on a particular tack without tacking. 'We are fetching the headland' means we can lay it on this tack.

A pyrotechnic signal device for attracting attention in an emergency. Types: handheld, parachute, smoke (day), and line-throwing.

The distance from the waterline to the deck edge. Higher freeboard means better reserve buoyancy.

A large headsail that overlaps the mast. Common ratios: Genoa 1 (biggest, light wind), Genoa 2, Genoa 3, and Genoa 4 (smallest, heavy wind).

A waterproof bag containing essential survival equipment — EPIRB, flares, water, food, torch, VHF — ready to grab in an abandonment situation.

The top edge of the vessel's side.

Turning the stern through the wind so the boom swings across from one side to the other. Under power this can be dangerous if unintentional.

Lines used to hoist sails up the mast. A halyard runs through a block at the masthead or along the forestay.

Stabilising the vessel's position by setting sails in opposition (usually headsail backed and mainsail aback) to slow to a near stop.

A cold downslope wind flowing from high ground to sea level, often strong in mountainous coastal areas.

The structural spine at the bottom of the hull, often weighted to resist heeling and provide lateral stability.

A strut or line connecting the boom to the mast or deck, controlling boom height and mainsail twist.

The imaginary line on which a vessel can sail directly to a windward mark without further tacking.

A network of lines from the mast to the boom that catch the mainsail as it is lowered, preventing it from falling overboard.

Two fixed lights (or marks) in line that, when aligned, indicate a safe channel or approach.

The sideways drift of a vessel caused by wind pressure on the hull and sails, pushing her off her intended course.

A buoyancy aid designed to keep an unconscious person's head above water. Should be worn at all times in exposed conditions.

The line that controls the angle of the boom and hence the mainsail's trim relative to the wind.

Emergency procedure for recovering a person who has fallen overboard, including immediate actions: throw flotation, keep person in sight, and execute a recovery maneuver.

The international voice distress signal, used only when life is in immediate danger. 'Mayday Mayday Mayday' is said three times.

The line used to secure the vessel to a mooring buoy or quay.

National Oceanic and Atmospheric Administration — source of charts, weather forecasts, and tide data (US).

A line that tensions the foot (bottom) of the mainsail along the boom, controlling foot camber.

The international urgency signal, used when there is a serious condition but no immediate danger to life (e.g., engine failure in traffic).

A plotting instrument with two hinged rules used to transfer bearings on a chart.

The vessel's heading relative to the wind direction — e.g., close-hauled, beam reach, broad reach, running.

Sailing with the wind coming over the port (left) side; the boom is on the starboard side.

To reduce sail area in strong wind by tying down part of the sail with reef points or a reef line.

Sailing directly downwind with the wind coming from directly astern.

A position obtained by taking bearings on the same object at different times while underway, using the vessel's course to move the earlier bearing forward.

Sailing as close to the wind as the vessel allows, typically 35–50° off the true wind direction.

A daytime wind blowing from sea to land, caused by heated air over land rising and drawing in cooler air from the sea.

Safety call broadcast to warn of navigational hazards or dangerous weather (pronounced 'seh-cur-it-ay').

Wire or rope running from the masthead (or spreaders) to the sides of the boat, preventing the mast from falling sideways.

Speed Over Ground — the actual speed of the vessel over the seabed, accounting for current and leeway.

Horizontal struts on the mast that hold the shrouds away from the mast, increasing the angle and thus the support.

A mooring line that runs roughly parallel to the quay, preventing the vessel from moving fore or aft.

A sudden violent gust of wind, often accompanied by rain. Can arrive with little warning and require instant sail reduction.

Sailing with the wind coming over the starboard (right) side; the boom is on the port side. Has right of way over port tack.

The aft end of the vessel.

A weather map showing isobars, fronts, and pressure systems across a wide area at a given time.

To turn the bow through the wind so the sails fill from the other side. Also refers to the windward course sailed between tacks.

A line from the masthead to the end of the boom that supports the boom when the mainsail is lowered.

Two objects appearing in line, used as a bearing indicator. 'The transit closes' means objects are aligning.

The flat surface forming the stern of a modern yacht.

A metal device for adjusting the tension of standing rigging wires.

See Kicker. Prevents the boom from rising and controls leech tension when sailing downwind.

A wind shifting in a clockwise direction (e.g., NE → E → SE). Opposite of backing.

Very High Frequency marine radio for ship-to-ship and ship-to-shore communication. Channel 16 is the international distress and calling channel.

The trail of disturbed water left behind a moving vessel.

A heavy-duty cleat designed for larger vessels and higher loads.

The line where the hull meets the surface of the water when the vessel is afloat.

The tendency of the vessel to turn into the wind. A slight weather helm is desirable; too much indicates excessive heeling or imbalance.

A cleat fixed to a wharf or dock for securing lines.

Running directly downwind with headsail poled out to one side and mainsail on the other.