The Collaborative International Dictionary of English v.0.48:

Peacock \Pea"cock`\ (p[=e]"k[o^]k`), n. [OE. pecok. Pea- in this
   word is from AS. pe['a], p[=a]wa, peacock, fr. L. pavo, prob.
   of Oriental origin; cf. Gr. taw`s, taw^s, Per. t[=a]us,
   t[=a]wus, Ar. t[=a]w[=u]s. See Cock the bird.]
   1. (Zool.) The male of any pheasant of the genus Pavo, of
      which at least two species are known, native of Southern
      Asia and the East Indies.
      [1913 Webster]

   Note: The upper tail coverts, which are long and capable of
         erection, are each marked with a black spot bordered by
         concentric bands of brilliant blue, green, and golden
         colors. The common domesticated species is Pavo
         cristatus. The Javan peacock (Pavo muticus) is more
         brilliantly colored than the common species.
         [1913 Webster]

   2. In common usage, the species in general or collectively; a
      peafowl.
      [1913 Webster]

   Peacock butterfly (Zool.), a handsome European butterfly
      (Hamadryas Io) having ocelli like those of peacock.

   Peacock fish (Zool.), the European blue-striped wrasse
      (Labrus variegatus); -- so called on account of its
      brilliant colors. Called also cook wrasse and cook.

   Peacock pheasant (Zool.), any one of several species of
      handsome Asiatic pheasants of the genus Polyplectron.
      They resemble the peacock in color.
      [1913 Webster]

WordNet (r) 3.0 (2006):

peacock
    n 1: European butterfly having reddish-brown wings each marked
         with a purple eyespot [syn: peacock, peacock butterfly,
         Inachis io]
    2: male peafowl; having a crested head and very large fanlike
       tail marked with iridescent eyes or spots

Moby Thesaurus II by Grady Ward, 1.0:

139 Moby Thesaurus words for "peacock":
   Dalmatian, antigorite, attitudinize, avifauna, baby bird, billy,
   billy goat, bird, bird of Jove, bird of Juno, bird of Minerva,
   bird of night, bird of passage, bird of prey, birdie, birdlife,
   birdy, boar, bubbly-jock, buck, bull, bullock, butterfly,
   cage bird, candy cane, chameleon, chanticleer, cheetah, chick,
   chrysotile, cock, cockerel, confetti, crazy quilt, cygnet,
   diving bird, dog, dove, drake, eagle, eaglet, entire, entire horse,
   firedog, fish-eating bird, fledgling, flightless bird, fowl,
   fruit-eating bird, fulmar, game bird, gander, gobbler, harlequin,
   hart, he-goat, insect-eating bird, iris, jaguar, leopard, mackerel,
   mackerel sky, marble, marbled paper, migrant, migratory bird,
   miles gloriosus, moire, mother-of-pearl, nacre, nestling, ocelot,
   opal, ophite, oscine bird, owl, passerine bird, patchwork quilt,
   peafowl, peahen, perching bird, pigeon, pontificate, pose,
   pose for effect, posture, prance, rainbow, ram, ratite, rooster,
   sea bird, seed-eating bird, serpentine, serpentine marble,
   shore bird, shot silk, songbird, spectrum, squab, stag, stalk,
   stallion, steer, storm petrel, stormy petrel, stot, strike a pose,
   strike an attitude, strut, strutter, stud, studhorse, swagger,
   swaggerer, swan, swank, swanker, swash, swashbuckle, swashbuckler,
   swasher, swell, tom, tom turkey, tomcat, top cow, top horse,
   tortoise shell, tup, turkey gobbler, turkey-cock, wading bird,
   warbler, water bird, waterfowl, wether, wildfowl, zebra



Easton's 1897 Bible Dictionary:

Peacock
   (Heb. tuk, apparently borrowed from the Tamil tokei). This bird
   is indigenous to India. It was brought to Solomon by his ships
   from Tarshish (1 Kings 10:22; 2 Chr. 9:21), which in this case
   was probably a district on the Malabar coast of India, or in
   Ceylon. The word so rendered in Job 39:13 literally means wild,
   tumultuous crying, and properly denotes the female ostrich
   (q.v.).