The Collaborative International Dictionary of English v.0.48:

Sawfish \Saw"fish`\, n. (Zool.)
   Any one of several species of elasmobranch fishes of the
   genus Pristis. They have a sharklike form, but are more
   nearly allied to the rays. The flattened and much elongated
   snout has a row of stout toothlike structures inserted along
   each edge, forming a sawlike organ with which it mutilates or
   kills its prey.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sawfish
    n 1: primitive ray with sharp teeth on each edge of a long
         flattened snout