The Collaborative International Dictionary of English v.0.48:

Gambusia \Gambusia\ n.
   A genus of fish including some of the mosquitofish.

   Syn: genus Gambusia.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Gambusia
    n 1: mosquitofish [syn: Gambusia, genus Gambusia]