luff

Short definition from Wiktionary

Noun

1. 1
   The vertical edge of a sail that is closest to the direction of the wind.
2. 2
   The act of sailing a ship close to the wind.
3. 3
   The roundest part of a ship's bow.
4. 4
   The forward or weather leech of a sail, especially of the jib, spanker, and other fore-and-aft sails.

Verb

1. 1
   To shake due to being trimmed improperly.
2. 2
   To bring the ship's head up closer to the wind. (Alternatively luff up)
3. 3
   to let out (a sail) so that it luffs.
4. 4
   To alter the vertical angle of the jib of a crane so as to bring it level with the load.

Proper noun

1. 1
   A surname.