cayman

from WordNet (r) 3.0 (2006)

cayman
    n 1: a semiaquatic reptile of Central and South America that
         resembles an alligator but has a more heavily armored belly
         [syn: {caiman}, {cayman}]

from The Collaborative International Dictionary of English v.0.48

Cayman \Cay"man\ (k[=a]"man), n. [From the language of Guiana:
   cf. Sp. caiman.] (Zool.)
   The south America alligator. See {Alligator}. [Sometimes
   written {caiman}.]
   [1913 Webster]