The Collaborative International Dictionary of English v.0.48:

Luff \Luff\ (l[u^]f), v. i. [imp. & p. p. Luffed (l[u^]ft); p.
   pr. & vb. n. Luffing.]
   1. (Naut.) To turn the head of a vessel toward the wind; to
      sail nearer the wind; to turn the tiller so as to make the
      vessel sail nearer the wind.
      [1913 Webster]

   2. (Naut.) To flutter or shake from being aligned close to
      the direction of the wind; -- said of a sail.
      [PJC]

   To luff round, or To luff alee, to make the extreme of
      this movement, for the purpose of throwing the ship's head
      into the wind.
      [1913 Webster]