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
Word origin
C17: from French, diminutive of Guillaume William
guillemot in American English
(ˈgɪləˌmɑt)
noun
any of various narrow-billed, northern alcidine shorebirds (genera Uria and Cepphus)