Auk \Auk\, n. [Prov. E. alk; akin to Dan. alke, Icel. & Sw. alka.] (Zool.) A name given to various species of arctic sea birds of the family {Alcid[ae]}. The great auk, now extinct, is {Alca impennis} (or {Plautus impennis}) . The razor-billed auk is {Alca torda}. See {Puffin}, {Guillemot}, and {Murre}. [1913 Webster]