flag officer

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

• noun An officer in the navy or coast guard holding a rank higher than captain, such as rear admiral, vice admiral, or admiral.

from The Century Dictionary.

• noun A naval officer privileged to display a flag denoting his rank; an admiral, vice-admiral, rear-admiral, or commodore.

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

• noun A naval officer with the rank of rear admiral or above, such officers are entitled to fly a personal flag, especially on the flagship.
• noun informal In addition to naval officers of Navy and the Coast Guard, a general officer in the Army, Marines, or Air Force with the rank of brigadier general or higher.

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

• noun a senior naval officer above the rank of captain