• Abeam: At a right angle to a boat’s length.
  • Anchor lines: Lines that attach an anchor to a boat.
  • Anemometer: An electronic wind gauge.
  • Astern: Behind a boat, or in reverse.
  • Bilge pump: Hydraulic pump for removing water from the lowest part of the boat.
  • Boom vang: A device that prevents the boom from rising or lowering.
  • Bosun’s chair: Seat used for going aloft.
  • Bow: The front section of the boat
  • Foredeck: The front section of the boat’s deck
  • Harden up: To turn toward the wind or sail closer to the wind.
  • Halyard: The line or wire for hoisting a sail.
  • Heave-to: To stop a sailing vessel by lashing the helm in opposition to the sails.
  • Helm: The wheel and/or wheelhouse area used to steer the boat.
  • Spreaders: Metal struts on the mast that hold the shrouds out from the mast.
  • Jib: A triangular foresail.
  • Jibe: To change tacks by steering away from the wind, the stern of the vessel turning through the wind
  • Jib sheet: A line attached to the jib to control it.
  • Lee: The side of the boat sheltered from the wind.
  • Lifeline (gate): An opening in the lines allowing for boarding the boat, also called gangway.
  • Luffing: The lead edge of a jib or mainsail. Also, to head into the wind, causing sails to flap and flutter.
  • Mainsail: The sail attached to and behind the mainmast.
  • Mast: A vertical pole supporting sails or rigging.
  • Midship line: The middle section of a boat.
  • Port: The left side of the boat (when facing forward).
  • Slip: A berth for a boat; a place for a boat to moor.
  • Spinnaker: A lightweight sail used downwind that often balloons in front of the boat.
  • Starboard: The right side of the boat (when facing forward).
  • Stern: The rear section of a boat.
  • Tack: The bottom front corner of a sail.
  • Tacking: A maneuver changing directions starboard and port by bringing the bow through the wind.
  • Thwart: A bench seat across the width of an open boat.
  • Topping lift: A line that supports the boom when the sail is not set.
  • Vee-birth: A cabin in the far forward section of the hull.
  • Windward: In the direction that the wind is coming from.

Sources: Sailing.about.com, Wikipedia, schoolofsailing.net, seatalk.info.