D defs.my
Entry 4 senses Webster, 1913

Commander

/kəm-ăn'-dẽr/ · Com·mand·er · IPA /kəˈmændɚ/
01 n. A chief; one who has supreme authority; a leader; the chief officer of an army, or of any division of it.
  1. 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. 2.
    An officer who ranks next below a captain, -- ranking with a lieutenant colonel in the army.(Navy)
  3. 3.
    The chief officer of a commandery.
  4. 4.
    A heavy beetle or wooden mallet, used in paving, in sail lofts, etc.
Phrases & compounds
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.