The Collaborative International Dictionary of English v.0.48:

Garfish \Gar"fish`\, n. [See Gar, n.] (Zool.)
   (a) A European marine fish (Belone vulgaris); -- called
       also gar, gerrick, greenback, greenbone,
       gorebill, hornfish, longnose, mackerel guide,
       sea needle, and sea pike.
   (b) One of several species of similar fishes of the genus
       Tylosurus, of which one species (T. marinus) is
       common on the Atlantic coast. T. Caribb[ae]us, a very
       large species, and T. crassus, are more southern; --
       called also needlefish. Many of the common names of the
       European garfish are also applied to the American
       species.
       [1913 Webster]

WordNet (r) 3.0 (2006):

garfish
    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]