The Collaborative International Dictionary of English v.0.48:

Snook \Snook\ (sn[=oo]k), v. i. [Prov. E. snook to search out,
   to follow by the scent; cf. Sw. snoka to lurk, LG.
   sn["o]ggen, snuckern, sn["o]kern, to snuffle, to smell about,
   to search for.]
   To lurk; to lie in ambush. [Obs.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Snook \Snook\, n. [D. snoek.] (Zool.)
   (a) A large perchlike marine food fish (Centropomus
       undecimalis) found both on the Atlantic and Pacific
       coasts of tropical America; -- called also ravallia,
       and robalo.
   (b) The cobia.
   (c) The garfish.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Robalo \Rob"a*lo\, n. [Sp. r['o]balo.]
   Any of several pikelike marine fishes of the West Indies and
   tropical America constituting the family Oxylabracidae,
   esp. the largest species (Oxylabrax undecimalis, syn.
   Centropomus undecimalis), a valuable food fish called also
   snook, the smaller species being called

WordNet (r) 3.0 (2006):

snook
    n 1: large tropical American food and game fishes of coastal and
         brackish waters; resemble pike