commander in chief

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The supreme commander of all the armed forces of a nation.
• noun The officer commanding a major armed force.

from The Century Dictionary.

• noun The commander of all the armies of a state or nation; the chief military commander.
• noun In the navy, a flag-officer commanding an independent fleet or squadron.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Supreme commander of the armed forces of an entire country.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the officer who holds the supreme command