The Collaborative International Dictionary of English v.0.48:

Macaw \Ma*caw"\, n. [From the native name in the Antilles.]
   (Zool.)
   Any parrot of the genus Ara, Sittace, or Macrocercus.
   About eighteen species are known, all of them found in
   Central and South America. They are large and have a very
   long tail, a strong hooked bill, and a naked space around the
   eyes. The voice is harsh, and the colors are brilliant and
   strongly contrasted; they are among the largest and showiest
   of parrots. Different species names have been given to the
   same macaw, as for example the Hyacinthine macaw, which has
   been variously classified as Anodorhyncus hyacynthinus,
   Anodorhyncus maximiliani, and Macrocercus hyacynthinus.
   [1913 Webster +PJC]
   [1913 Webster]

   Macaw bush (Bot.), a West Indian name for a prickly kind of
      nightshade (Solanum mammosum).

   Macaw palm, Macaw tree (Bot.), a tropical American palm
      (Acrocomia fusiformis and other species) having a
      prickly stem and pinnately divided leaves. Its nut yields
      a yellow butter, with the perfume of violets, which is
      used in making violet soap. Called also grugru palm.
      [1913 Webster]

WordNet (r) 3.0 (2006):

macaw
    n 1: long-tailed brilliantly colored parrot of Central America
         and South America; among the largest and showiest of
         parrots