a black or brown-speckled seabird of the genus Cepphus, of northern seas, having a sharply pointed black bill, red legs, and white wing patches, as C. grylle(black guillemot) of the North Atlantic and the similar C. columba(pigeon guillemot) of the North Pacific.
2.
British. a murre of the genus Uria.
Origin: 1670–80; < French, apparently diminutive of Guillaume William
any northern oceanic diving bird of the genera Uria and Cepphus, having a black-and-white plumage and long narrow bill: family Alcidae (auks, etc), order Charadriiformes
[C17: from French, diminutive of Guillaume William]