The Collaborative International Dictionary of English v.0.48:

Billfish \Bill"fish`\ (b[i^]l"f[i^]sh`), n. (Zool.)
   A name applied to several distinct fishes:
   (a) The garfish (Tylosurus longirostris, or Belone
       longirostris) and allied species.
   (b) The saury, a slender fish of the Atlantic coast
       (Scomberesox saurus).
   (c) The Tetrapturus albidus, a large oceanic species
       related to the swordfish; the spearfish.
   (d) The American fresh-water garpike (Lepidosteus osseus).
       [1913 Webster]