any large, web-footed, seabird of the family Sulidae, having a sharply pointed bill, long wings, and a wedge-shaped tail, noted for its plunging dives for fish.
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.
