Source : Webster's Revised Unabridged Dictionary (1913)

Auk \Auk\, n. [Prov. E. alk; akin to Dan. alke, Icel. & Sw.
   alka.] (Zo["o]l.)
   A name given to various species of arctic sea birds of the
   family {Alcid[ae]}. The great auk, now extinct, is {Alca (or
   Plautus) impennis}. The razor-billed auk is {A. torda}. See
   {Puffin}, {Guillemot}, and {Murre}.

Source : WordNet®

auk
     n : black-and-white short-necked web-footed diving bird of
         northern seas