Commodore \Com"mo*dore`\, n. [Prob. a corruption of commander, or Sp. comendador a knight of a military order who holds a commandery; also a superior of a monastery, fr. LL. commendare to command. Cf. Commend, Command, Commander.]

1. (U. S. Navy) An officer who ranks next above a captain; sometimes, by courtesy, the senior captain of a squadron. The rank of commodore corresponds with that of brigadier general in the army.

2. (British Navy) A captain commanding a squadron, or a division of a fleet, or having the temporary rank of rear admiral.

3. A title given by courtesy to the senior captain of a line of merchant vessels, and also to the chief officer of a yachting or rowing club.

4. A familiar for the flagship, or for the principal vessel of a squadron or fleet.

Source: Webster's Revised Unabridged Dictionary (1913)