Source : Webster's Revised Unabridged Dictionary (1913)

Gar \Gar\, n. [Prob. AS. g[=a]r dart, spear, lance. The name is
   applied to the fish on account of its long and slender body
   and pointed head. Cf. {Goad}, {Gore}, v.] (Zo["o]l.)
   (a) Any slender marine fish of the genera {Belone} and
       {Tylosurus}. See {Garfish}.
   (b) The gar pike. See {Alligator gar} (under {Alligator}),
       and {Gar pike}.

   {Gar pike}, or {Garpike} (Zo["o]l.), a large, elongated
      ganoid fish of the genus {Lepidosteus}, of several
      species, inhabiting the lakes and rivers of temperate and
      tropical America.

Gar \Gar\, v. t. [Of Scand. origin. See {Gear}, n.]
   To cause; to make. [Obs. or Scot.] --Spenser.

Source : WordNet®

gar
     n 1: primitive predaceous North American fish covered with hard
          scales and having long jaws with needle-like teeth [syn:
           {garfish}, {garpike}, {billfish}, {Lepisosteus osseus}]
     2: elongate European surface-dwelling predacious fishes with
        long toothed jaws; abundant in coastal waters [syn: {needlefish},
         {billfish}]