Mer‐gan″ser (?), n. [Sp. mergánsar, fr. mergo a diver (L. mergus, fr. mergere to dip, dive) + ánsar goose, L. anser.] (Zoöl.) Any bird of the genus Merganser, and allied genera. They are allied to the ducks, but have a sharply serrated bill.
☞ The red-breasted merganser (Merganser serrator) inhabits both hemispheres. It is called also sawbill, harle, and sheldrake. The American merganser (M. Americanus.) and the hooded merganser (Lophodytes cucullatus) are well-known species. — White merganser, the smew or white nun.