The Collaborative International Dictionary of English v.0.48:

Spearfish \Spear"fish`\, n. (Zool.)
   (a) A large and powerful fish (Tetrapturus albidus) related
       to the swordfish, but having scales and ventral fins. It
       is found on the American coast and the Mediterranean.
   (b) The carp sucker.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quillback \Quill"back`\, n. (Zool.)
   An American fresh-water fish (Ictiobus cyprinus syn.
   Carpiodes cyprinus); -- called also carp sucker,
   sailfish, spearfish, and skimback.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spearfish
    n 1: any of several large vigorous pelagic fishes resembling
         sailfishes but with first dorsal fin much reduced;
         worldwide but rare