Source : Webster's Revised Unabridged Dictionary (1913)

Corsair \Cor"sair\, n. (Zo["o]l.)
   A Californian market fish ({Sebastichthys rosaceus}).

Corsair \Cor"sair\ (k?r"s?r), n. [F. corsaire (cf. It. corsare,
   corsale, Pr. corsari), LL. corsarius, fr. L. cursus a
   running, course, whence Sp. corso cruise, corsa cruise,
   coasting voyage, corsear to cruise against the enemy, to
   pirate, corsario cruising, a privateer authorized to cruise
   against the enemy. See {Course}.]
   1. A pirate; one who cruises about without authorization from
      any government, to seize booty on sea or land.

   2. A piratical vessel.

            Barbary corsairs . . . infested the coast of the
            Mediterranean.                        --Prescott.

Source : WordNet®

corsair
     n 1: a pirate along the Barbary coast [syn: {Barbary pirate}]
     2: a swift pirate ship (often operating with official sanction)