The Collaborative International Dictionary of English v.0.48:

Loof \Loof\ (l[=oo]f or l[u^]f; 277), n. [See Luff.] [Also
   written luff.] (Naut.)
   (a) Formerly, some appurtenance of a vessel which was used in
       changing her course; -- probably a large paddle put over
       the lee bow to help bring her head nearer to the wind.
   (b) The part of a ship's side where the planking begins to
       curve toward bow and stern.
       [1913 Webster]

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]

The Collaborative International Dictionary of English v.0.48:

Luff \Luff\ (l[u^]f), n. [OE. lof, prob. a sort of timber by
   which the course of a ship was directed, perh. a sort of
   paddle; cf. D. loef luff, loeven to luff. The word is perh.
   akin to E. glove. Cf. Aloof.] (Naut.)
      (a) The side of a ship toward the wind.
      (b) The act of sailing a ship close to the wind.
      (c) The roundest part of a ship's bow.
      (d) The forward or weather leech of a sail, especially of
          the jib, spanker, and other fore-and-aft sails.
          [1913 Webster]

   Luff tackle, a purchase composed of a double and single
      block and fall, used for various purposes. --Totten.

   Luff upon luff, a luff tackle attached to the fall of
      another luff tackle. --R. H. Dana, Jr.
      [1913 Webster]

WordNet (r) 3.0 (2006):

luff
    n 1: (nautical) the forward edge of a fore-and-aft sail that is
         next to the mast
    2: the act of sailing close to the wind
    v 1: sail close to the wind [syn: luff, point]
    2: flap when the wind is blowing equally on both sides; "the
       sails luffed"