stegosaurus

from WordNet (r) 3.0 (2006)

stegosaurus
    n 1: herbivorous ornithischian dinosaur with a row of bony
         plates along its back and a spiked tail probably used as a
         weapon [syn: {stegosaur}, {stegosaurus}, {Stegosaur
         stenops}]

from The Collaborative International Dictionary of English v.0.48

Stegosaurus \Steg`o*sau"rus\ (st[e^]g`[-o]*s[add]"r[u^]s), n.
   [NL., fr. Gr. ste`gh roof + say^ros a lizard.] (Paleon.)
   A genus of large Jurassic dinosaurs remarkable for a powerful
   dermal armature of plates and spines.
   [1913 Webster]