Source : Webster's Revised Unabridged Dictionary (1913)

Privateer \Pri`va*teer"\, v. i. [imp. & p. p. {Privateered}; p.
   pr. & vb. n. {Privateering}.]
   To cruise in a privateer.

Privateer \Pri`va*teer"\, n. [From {Private}.]
   1. An armed private vessel which bears the commission of the
      sovereign power to cruise against the enemy. See {Letters
      of marque}, under {Marque}.

   2. The commander of a privateer.

            Kidd soon threw off the character of a privateer and
            became a pirate.                      --Macaulay.

Source : WordNet®

privateer
     n 1: an officer or crew member of a privateer [syn: {privateersman}]
     2: a privately owned warship commissioned to prey on the
        commercial shipping or warships of an enemy nation