The Collaborative International Dictionary of English v.0.48:

Gar pike \Gar" pike`\ or Garpike \Gar"pike`\ (Zool.)
   See under Gar.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

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.] (Zool.)
   (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.
       [1913 Webster]

   Gar pike, or Garpike (Zool.), a large, elongated ganoid
      fish of the genus Lepidosteus, of several species,
      inhabiting the lakes and rivers of temperate and tropical
      America.
      [1913 Webster]

WordNet (r) 3.0 (2006):

garpike
    n 1: primitive predaceous North American fish covered with hard
         scales and having long jaws with needlelike teeth [syn:
         gar, garfish, garpike, billfish, Lepisosteus
         osseus]