The Collaborative International Dictionary of English v.0.48:

Iguanodon \I*gua"no*don\, n. [Iguana + Gr. ?, ?, a tooth.]
   (Paleon.)
   A genus of gigantic herbivorous dinosaurs having a birdlike
   pelvis and large hind legs with three-toed feet capable of
   supporting the entire body. Its teeth resemble those of the
   iguana, whence its name. Several species are known, mostly
   from the Wealden of England and Europe. See Illustration in
   Appendix.
   [1913 Webster]

WordNet (r) 3.0 (2006):

iguanodon
    n 1: massive herbivorous bipedal dinosaur with a long heavy
         tail; common in Europe and northern Africa; early
         Cretaceous period