The Collaborative International Dictionary of English v.0.48:

Jay \Jay\, n. [F. geai, OF. gai, jaj, perh. fr. OHG. g[=a]hi.
   Cf. Gay.] (Zool.)
   Any one of the numerous species of birds belonging to
   Garrulus, Cyanocitta, and allied genera of the family
   Corvidae. They are allied to the crows, but are smaller,
   more graceful in form, often handsomely colored, and usually
   have a crest.
   [1913 Webster]

   Note: The European jay (Garrulus glandarius) is a large and
         handsomely colored species, having the body pale
         reddish brown, lighter beneath; tail and wing quills
         blackish; the primary coverts barred with bright blue
         and black; throat, tail coverts, and a large spot on
         the wings, white. Called also jay pie, Jenny jay,
         and k[ae]. The common blue jay (Cyanocitta
         cristata.), and the related species, are brilliantly
         colored, and have a large erectile crest. The
         California jay (Aphelocoma Californica), the Florida
         jay (Aphelocoma Floridana), and the green jay
         (Xanthoura luxuosa), of Texas and Mexico, are large,
         handsome, crested species. The Canada jay (Perisoreus
         Canadensis), and several allied species, are much
         plainer and have no crest. See Blue jay, and Whisky
         jack.
         [1913 Webster]

   Jay thrush (Zool.), any one several species of Asiatic
      singing birds, of the genera Garrulax, Grammatoptila,
      and related genera of the family Crateropodid[ae]; as,
      the white-throated jay thrush (Garrulax albogularis)
      (also called the white-throated laughingthrush), of
      India.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Cyanocitta cristata
    n 1: common jay of eastern North America; bright blue with grey
         breast [syn: blue jay, jaybird, Cyanocitta cristata]