The Collaborative International Dictionary of English v.0.48:
Redhead \Red"head`\ (-h?d`), n.
1. A person having red hair.
(a) An American duck (Aythya Americana) highly esteemed
as a game bird. It is closely allied to the
canvasback, but is smaller and its head brighter red.
Called also red-headed duck. American poachard,
grayback, and fall duck. See Illust. under
(b) The red-headed woodpecker. See Woodpecker.
3. (Bot.) A kind of milkweed (Asclepias Curassavica) with
red flowers. It is used in medicine.