Source : Webster's Revised Unabridged Dictionary (1913)

Merganser \Mer*gan"ser\, n. [Sp. merg['a]nsar, fr. mergo a diver
   (L. mergus, fr. mergere to dip, dive) + ['a]nsar goose, L.
   anser.] (Zo["o]l.)
   Any bird of the genus {Merganser}, and allied genera. They
   are allied to the ducks, but have a sharply serrated bill.

   Note: 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.

Source : WordNet®

Lophodytes cucullatus
     n : small North American duck with a high circular crest on the
         male's head [syn: {hooded merganser}, {hooded sheldrake}]