a sail (or either of a pair of sails) immediately above the lowermost sail of a mast and supported by a topmast
source: WordNet 3.0
In a square-rigged vessel, the sail next above the lowermost sail on a mast. This sail is the one most frequently reefed or furled in working the ship. In a fore-and-aft rigged vessel, the sail set upon and above the gaff. See Cutter, Schooner, Sail, and Ship.
