Source : Webster's Revised Unabridged Dictionary (1913)

Commander \Com*mand"er\, n. [Cf. F. commandeur. Cf. {Commodore},
   {Commender}.]
   1. A chief; one who has supreme authority; a leader; the
      chief officer of an army, or of any division of it.

            A leader and commander to the people. --Is. lv. 4.

   2. (Navy) An officer who ranks next below a captain, --
      ranking with a lieutenant colonel in the army.

   3. The chief officer of a commandery.

   4. A heavy beetle or wooden mallet, used in paving, in sail
      lofts, etc.

   {Commander in chief}, the military title of the officer who
      has supreme command of the land or naval forces or the
      united forces of a nation or state; a generalissimo. The
      President is commander in chief of the army and navy of
      the United States.

   Syn: See {Chief}.

Source : WordNet®

commander in chief
     n : the officer who holds the supreme command; "in the U.S. the
         president is the commander in chief" [syn: {generalissimo}]