The Collaborative International Dictionary of English v.0.48:

Xiphius \Xiph"i*us\, n. [NL., fr. Gr. xi`fos a sword.] (Zool.)
   A genus of cetaceans having a long, pointed, bony beak,
   usually two tusklike teeth in the lower jaw, but no teeth in
   the upper jaw.
   [1913 Webster]