The Collaborative International Dictionary of English v.0.48:

Dinosauria \Di`no*sau"ri*a\, n. pl. [NL., fr. Gr. ? terrible + ?
   lizard.] (Paleon.)
   An order of extinct mesozoic reptiles, mostly of large size
   (whence the name). Notwithstanding their size, they present
   birdlike characters in the skeleton, esp. in the pelvis and
   hind limbs. Some walked on their three-toed hind feet, thus
   producing the large "bird tracks," so-called, of mesozoic
   sandstones; others were five-toed and quadrupedal. See
   Illust. of Compsognathus, also Illustration of Dinosaur in
   Appendix. Dinothere