The Collaborative International Dictionary of English v.0.48:

Turkey \Tur"key\ (t[^u]r"k[=e]), n.; pl. Turkeys. [So called
   because it was formerly erroneously believed that it came
   originally from Turkey: cf. F. Turquie Turkey. See Turk.]
   (Zool.)
   Any large American gallinaceous bird belonging to the genus
   Meleagris, especially the North American wild turkey
   (Meleagris gallopavo), and the domestic turkey, which was
   probably derived from the Mexican wild turkey, but had been
   domesticated by the Indians long before the discovery of
   America.
   [1913 Webster]

   Note: The Mexican wild turkey is now considered a variety of
         the northern species (var. Mexicana). Its tail feathers
         and coverts are tipped with white instead of brownish
         chestnut, and its flesh is white. The Central American,
         or ocellated, turkey (Meleagris ocellata) is more
         elegantly colored than the common species. See under
         Ocellated. The Australian, or native, turkey is a
         bustard (Choriotis australis). See under Native.
         [1913 Webster]

   Turkey beard (Bot.), a name of certain American perennial
      liliaceous herbs of the genus Xerophyllum. They have a
      dense tuft of hard, narrowly linear radical leaves, and a
      long raceme of small whitish flowers. Also called
      turkey's beard.

   Turkey berry (Bot.), a West Indian name for the fruit of
      certain kinds of nightshade (Solanum mammosum, and
      Solanum torvum).

   Turkey bird (Zool.), the wryneck. So called because it
      erects and ruffles the feathers of its neck when
      disturbed. [Prov. Eng.]

   Turkey buzzard (Zool.), a black or nearly black buzzard
      (Cathartes aura), abundant in the Southern United
      States. It is so called because its naked and warty head
      and neck resemble those of a turkey. It is noted for its
      high and graceful flight. Called also turkey vulture.

   Turkey cock (Zool.), a male turkey.

   Turkey hen (Zool.), a female turkey.

   Turkey pout (Zool.), a young turkey. [R.]

   Turkey vulture (Zool.), the turkey buzzard.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Buzzard \Buz"zard\ (b[u^]z"z[~e]rd), n.[O.E. busard, bosard, F.
   busard, fr. buse, L. buteo, a kind of falcon or hawk.]
   [1913 Webster]
   1. (Zool.) A bird of prey of the Hawk family, belonging to
      the genus Buteo and related genera.
      [1913 Webster]

   2. (Zool.) In the United States, a term used for the turkey
      vulture (Cathartes aura), and sometimes
      indiscriminately to any vulture.
      [PJC]

   Note: The Buteo vulgaris is the common buzzard of Europe.
         The American species (of which the most common are
         Buteo borealis, Buteo Pennsylvanicus, and Buteo
         lineatus) are usually called hen hawks. -- The
         rough-legged buzzard, or bee hawk, of Europe (Pernis
         apivorus) feeds on bees and their larv[ae], with other
         insects, and reptiles. -- The moor buzzard of Europe is
         Circus [ae]ruginosus. See Turkey buzzard, and
         Carrion buzzard.
         [1913 Webster]

   Bald buzzard, the fishhawk or osprey. See Fishhawk.
      [1913 Webster]

   2. A blockhead; a dunce.
      [1913 Webster]

            It is common, to a proverb, to call one who can not
            be taught, or who continues obstinately ignorant, a
            buzzard.                              --Goldsmith.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Cathartes aura
    n 1: a New World vulture that is common in South America and
         Central America and the southern United States [syn:
         buzzard, turkey buzzard, turkey vulture, Cathartes
         aura]