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.
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.
2. In common usage, the species in general or collectively; a
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.