Source : Webster's Revised Unabridged Dictionary (1913)

Rook \Rook\, n. [AS. hr[=o]c; akin to OHG. hruoh, ruoh, ruoho,
   Icel. hr[=o]kr, Sw. roka, Dan. raage; cf. Goth. hrukjan to
   crow.]
   1. (Zo["o]l.) A European bird ({Corvus frugilegus})
      resembling the crow, but smaller. It is black, with purple
      and violet reflections. The base of the beak and the
      region around it are covered with a rough, scabrous skin,
      which in old birds is whitish. It is gregarious in its
      habits. The name is also applied to related Asiatic
      species.

            The rook . . . should be treated as the farmer's
            friend.                               --Pennant.

   2. A trickish, rapacious fellow; a cheat; a sharper.
      --Wycherley.

Source : WordNet®

Corvus frugilegus
     n : common gregarious Old World bird about the size and color of
         the American crow [syn: {rook}]