an Asian game fowl (Phasianus colchicus) with a whitish collar around the neck in the male, now widely introduced and bred in North America, Europe, etc.
See ring-necked pheasant in American Heritage Dictionary 4
noun
A widely distributed bird (Phasianus colchicus) native to the Old World, the male of which has a long pointed tail, brightly colored plumage, and a white ring around the neck.