Source : Webster's Revised Unabridged Dictionary (1913)

Gaff \Gaff\, n. [OE. gaffe, F. gaffe an iron hook with which
   seamen pull great fishes into their ships; cf. Ir. gaf, gafa
   hook; perh. akin to G. gabel fork, Skr. gabhasti. Cf.
   {Gaffle}, {Gable}.]
   1. A barbed spear or a hook with a handle, used by fishermen
      in securing heavy fish.

   2. (Naut.) The spar upon which the upper edge of a
      fore-and-aft sail is extended.

   3. Same as {Gaffle}, 1. --Wright.

Gaff \Gaff\, v. t. [imp. & p. p. {Gaffed}; p. pr. & vb. n.
   {Gaffing}.]
   To strike with a gaff or barbed spear; to secure by means of
   a gaff; as, to gaff a salmon.

Source : WordNet®

gaff
     n 1: a spar rising aft from a mast to support the head of a
          quadrilateral fore-and-aft sail
     2: an iron hook with a handle; used for landing large fish