luff

Etymology

From Old French lof. Collins English Dictionary states that this word is ultimately derived from Middle Dutch loef. Ellert Ekwall's Shakspere's Vocabulary: its etymological elements (1903) related this verb and loof instead to the East Frisian verb lofen, lufen, which would make it cognate to the French term lover.

noun

1. (nautical) The vertical edge of a sail that is closest to the direction of the wind.
   By easing the halyard, the luff of the sail was made to sag to leeward.
   The man at the helm was watching the luff of the sail and whistling away gently to himself. 1883, Robert Louis Stevenson, Treasure Island
2. (nautical) The act of sailing a ship close to the wind.
3. (nautical) The roundest part of a ship's bow.
4. (nautical) The forward or weather leech of a sail, especially of the jib, spanker, and other fore-and-aft sails.

verb

1. (nautical, of a sail, intransitive) To shake due to being trimmed improperly.
   I thought how my life is like a little boat and I must hold the tiller steady against the buffeting of wind and waves, and how sometimes, like this morning, I lose my hold somehow and the sail luffs helplessly and the little vessel wallows, turning this way and that in the swell. 1993, John Banville, Ghosts
2. (nautical, of sailing vessels, intransitive) To bring the ship's head up closer to the wind. (Alternatively luff up)
   Helm there! Luff, luff a point! So; steady, man, steady! 1851, Herman Melville, Moby Dick
3. (nautical, transitive) to let out (a sail) so that it luffs.
4. (mechanical) To alter the vertical angle of the jib of a crane so as to bring it level with the load.
   The tower is mounted on a slewing platform, which also carries the power plant and the counterweights, while the jib is supported and luffed by fixed pendant ropes. 1999, Howard I. Shapiro, Jay P. Shapiro, Lawrence K. Shapiro, Cranes and Derricks, page 95