1. any of various usually white herons having long plumes during breeding season;
The Collaborative International Dictionary of English v.0.48:
Egret \E"gret\, n. [See Aigret, Heron.]
1. (Zo["o]l.) The name of several species of herons which
bear plumes on the back. They are generally white. Among
the best known species are the American egret (Ardea
egretta syn. Herodias egretta); the great egret (Ardea
alba); the little egret (Ardea garzetta), of Europe;
and the American snowy egret (Ardea candidissima).
A bunch of egrets killed for their plumage. --G. W.
2. A plume or tuft of feathers worn as a part of a headdress,
or anything imitating such an ornament; an aigrette.
3. (Bot.) The flying feathery or hairy crown of seeds or
achenes, as the down of the thistle.
4. (Zo["o]l.) A kind of ape.
WordNet (r) 3.0 (2006):
n 1: any of various usually white herons having long plumes
during breeding season