A

Abaft

Toward the stern of a boat, or behind it.

Abeam

At right angles to the centreline of a boat.

Adrift

Floating without any means of propulsion, and without >mooring.

Aft

At, near, or toward the stern of a boat.

Aground

When a boat is stranded on the shore, or on the bottom of the body of water, it is said to have run aground.

Alee

Toward the opposite to the source of the wind side of a boat.

Aloft

Overhead.

Amidships

In the middle of the boat

Aport

To the port side of the boat.

Apparent wind

The combination of the true wind and the wind caused by the boat's own speed. This is the wind felt on the boat, as well as the one shown by the telltales.

Ashore

To be on or to go to the shore.

Astern

Toward the boat's stern.

Autopilot

A device - may be electronic or mechanical - used for keeping the boat on course without having to steer it (the same idea as on airplanes). It uses a compass, and is attached to the boat's steering mechanism.

B

Backing wind

A change in wind direction running counterclockwise, as in from west to southwest. 

Backstay

A rigging wire used to keep the mast from moving forward, as well as to vary the amount of bend in the mast.

Backwinded

If your sails are filled with the wind on the opposite side to what you want (for example, if they are trimmed for the starboard tack, but you get the wind from the port side), you are said to be backwinded.

Bail

To get rid of water accumulated in the boat.

Ballast

A very heavy material, such as lead or iron, placed in the keel of the boat, or in the bilge. It is used to provide stability. Oftentimes the crew is also a ballast - especially on smaller boats, or in a jocular way.

Battens

Thin strips of wood or plastic inserted into batten pockets used to stiffen the leech (to preserve the shape of the sail).

Beam

The widest part of a boat.

Bearing

A direction an object is relative to the observer (based on the compass heading).

Block

A pulley - a nautical term. Often with more than one wheel (sheave being the proper name) to increase its mechanical advantage.

oom

A spar (a wooden or metal pole) attached to the mast at a right angle, used to support the foot of a sail.

Bow

The front end of a boat.

Bowsprit

A spar that's attached to the bow of a boat, along the of the boat. The forestay can be attached to it - thus allowing for a greater sail area.

Breakers

Waves that have entered a shallow water, and built up in height. By doing this they "break" at the crest, producing a curled up formation.

C

-Centerboard

A pivoting board that prevents the boat from sliding sideways.

Centerline

The center of the boat: from the stern to the bow.

Chart

A nautically specialized map.

Cleat

A fitting for securing a line. It can be wooden, metal or nylon.

Clew

An aft corner of a triangular sail.

Cockpit

The rear area of the boat from where the crew operates.

D

Deck

A permanent covering over the hull of the boat.

E

Ensign

A flag indicating the nationality of the vessel.

F

Fairlead

A piece of hardware or equipment (such as a block) used for leading the jib sheets from the deck to the cockpit. They are located astern of the beam, on each side of the boat.

Foil

An attachment on the forestay, comprising a groove into which the luff of the jib can be fed.

Foot

The bottom edge of the sail - the one attached to the boom.

Foresail

A foresail is the sail (such as a jib) located immediately in front of the main mast.   It is attached to the forestay.

Forestay (sometimes called a jibstay, or a headstay)

A cable supporting the mast, running from the bow to the top of the mast.

G

Give-way vessel

A boat that has to stay clear of the right-of-way, or stand-on boat.

Gunwale

The top edge of the side of the hull.

H

Hatch

A small opening with a "door" on deck, allowing entry under the deck.

 

Halyard

A line used to raise things on a boat, for example "the main halyard" is the line used to raise the mainsail. It is a part of running rigging.

Head

The top part of a triangular sail. OR A toilet in a cruiser boat.

Headsail

Any sail located in front of the main mast.

Hull

The body of the boat.

I

J

Jib

The front sail.

Jibsheet

The line used to pull the jib in or let it out.

K

Keel

A weighted extension of a boat below it that prevents the boat from sliding sideways.

Knot

A nautical term for speed: one nautical mile per hour. Also a term indicating a method of tying a line.

L

Lash

To tie something using a light rope.

Leech

The aft edge of the triangular sail - the one that's not attached to anything.

Leeward (pronounced loo'ard)

The direction to which the wind is blowing.

Luff

The fore edge of a sail.

Luff up

To luff up means to bring the boat's bow so close to the wind, that the leech of the sail begins to flap.

M

Mainsail

boomed sail projecting aft from the mast

Mainsheet

The line used to pull the mainsail in or let it out.

Mast

The pole attached to the deck at the right angle, holding up the sails.

Masthead

The top of the mast.

Mizzen

The sail set on the second (aftermost, or rear) mast - as on a ketch.

Mooring

Permanent anchorage.   It consists of a heavy weight (or an anchor), a chain of a certain length, and a buoy. Mooring is also often used for piers, instead of pilings.

N

Nautical almanac

A book containing all current data: navigational, tidal, astronomical and so on. It is published annually.

O

Outhaul

A device located on the aft part of the boom, used to secure the clew, so that the foot is kept tense.

P

Q

Pier

A wooden structure (although it may be built from other materials) built over the water, used by boats for landing.

Piling

A thick post supporting or mooring a dock or pier. It is deep inside the seabed, and it projects above the water level.

Port Side

The left side of the boat.

R

Range

The distance between two objects (horizontally).

Rigging

The assembly of the boat.

Rudder

The underwater, movable plate used for steering, and for providing resistance to sideways motion caused by waves and wind. It is being controlled by the helmsman (helmsperson?) with a help of a tiller or a steering wheel.

S

Shackle

Part of the indispensable equipment on the boat. It is a small device used for attaching lines to other things, like sails.

Sheet

A line used to trim sails.

Shroud

The wires holding the mast at the sides.

Spar

A general name for all masts, booms, gaffs, and bowsprits.

Spreaders

The wooden or metal struts that are attached horizontally to the upper section of the mast, on both sides. They widen the angle of the shrouds, and thus provide a better support for the mast.

Stand-on vessel

A boat that has the right-of-way over the give-way vessel. It must maintain its course and speed.

Starboard Side

The right side of the boat.

Stays

Wires supporting the mast - fore and aft.

Stern

The back of the boat.

Surf

A continuous line of breakers at the shore.

T

Tack

The fore corner of a triangular sail.

Telltales

Short pieces of yarn attached to the shrouds, or the sails. At the shrouds they indicate the direction of the wind (the apparent wind ), and at the sails they help to check the air flow over the sail, so that proper trimming is easier.

Tiller

A spar attached to the rudder by the rudder head, used to control the direction of the boat. Another possibility for steering mechanism is a steering wheel.

Trampoline

The space on a catamaran, usually made of some kind of mesh, located between the two hulls. It's a place for the crew (like a cockpit on dinghies and cruisers).

Traveler

A track (usually metal) with a fixture sliding on it. The fixture holds the main sheet (usually), and the sliding allows for changing angles of the sail.

True wind

The strength and direction of the actual wind blowing. While sailing, the true wind is never felt - it is always a combination of the true wind, and the boat's speed (called the apparent wind ), and it is always a little forward to the true wind.

Trysail

A very small sail, used in a very heavy weather instead of a mainsail.

U

V

W

Winch

A mechanical device used to assist in pulling on lines. It is a reel-like part of the hardware.

Windward

The direction from which the wind is blowing.

Z

Zigzagging

Alternating tacks on approximately equal distances.