The Collaborative International Dictionary of English v.0.48:

Pollack \Pol"lack\, n. [Cf. G. & D. pollack, and Gael. pollag a
   little pool, a sort of fish.] (Zool.)
   (a) A marine gadoid food fish of Europe (Pollachius
       virens). Called also greenfish, greenling, lait,
       leet, lob, lythe, and whiting pollack.
   (b) The American pollock; the coalfish.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pollock \Pol"lock\, n. [See Pollack.] (Zool.)
   A marine gadoid fish (Pollachius carbonarius), native both
   of the European and American coasts. It is allied to the cod,
   and like it is salted and dried. In England it is called
   coalfish, lob, podley, podling, pollack, etc.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Pollack
    n 1: United States filmmaker (born in 1934) [syn: Pollack,
         Sydney Pollack]
    2: lean white flesh of North Atlantic fish; similar to codfish
       [syn: pollack, pollock]
    3: important food and game fish of northern seas (especially the
       northern Atlantic); related to cod [syn: pollack,
       pollock, Pollachius pollachius]