The Collaborative International Dictionary of English v.0.48:

Homonym \Hom"o*nym\, n. [Cf. F. homonyme. See Homonymous.]
   A word having the same sound as another, but differing from
   it in meaning; as the noun bear and the verb bear. [Written
   also homonyme.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

homonym
    n 1: two words are homonyms if they are pronounced or spelled
         the same way but have different meanings