cap·er·cail·lie (kāp'ər-kāl'yē, -kā'lē) n. A large grouse (Tetrao urogallus), native to northern Europe and having dark plumage and a fanlike tail. Also called wood grouse.
[Scottish Gaelic capull coille : capull, horse (from Middle Irish capall, from Old Irish, ultimately from Latin caballus, of Celtic origin) + coille, genitive of coille, forest (from Old Irish caill).]