The Collaborative International Dictionary of English v.0.48:

Ceratosaurus \Cer`a*to*sau"rus\, n. [NL., fr. Gr. ke`ras a horn
   + ? lizard.] (Paleon.)
   A swift-running bipedal carnivorous American Jurassic
   dinosaur allied to the European Megalosaurus. The animal was
   nearly twenty feet in length, and the skull bears a bony
   short horn between the nostrils on the united nasal bones.
   See Illustration in Appendix.
   [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

ceratosaurus
    n 1: primitive medium-sized theropod; swift-running bipedal
         carnivorous dinosaur having grasping hands with sharp claws
         and a short horn between the nostrils; Jurassic in North
         America [syn: ceratosaur, ceratosaurus]