The common Holarctic wild duck, Anas platyrhynchos, the male of which has a dark green head and a purplish-brown breast. Also: †the domesticated…

a duck belonging to any of numerous undomesticated species.

(a) the mallard, Anas platyrhynchos; (b) U.S. the hooded merganser, Mergus cucullatus.

A young wild duck or partridge.

A person who or animal which paddles about in mud, shallow water, etc. Also figurative.

Any of various other wild ducks, spec. a diving duck of the genus Aythya. Also with distinguishing word. Cf. pochard, n., scaup, n.