The Collaborative International Dictionary of English v.0.48:

budgerigar \budg"er*i*gar\, budgereegah \budgereegah\,
budgerygah \budgerygah\n.
   small Australian parakeet (Melopsittacus undulatus) usually
   light green with black and yellow markings in the wild but
   bred in many colors.

   Syn: budgie, grass parakeet, lovebird, shell parakeet.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

budgerygah
    n 1: small Australian parakeet usually light green with black
         and yellow markings in the wild but bred in many colors
         [syn: budgerigar, budgereegah, budgerygah, budgie,
         grass parakeet, lovebird, shell parakeet,
         Melopsittacus undulatus]