a person having red hair.-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 poachard.-the red-headed woodpecker. see woodpecker.-a kind of milkweed (asclepias curassavica) with red flowers. it is used in medicine.