sergeant major

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

• noun Used as a title for a noncommissioned officer serving as chief administrative assistant of a headquarters unit of the US Army or Marine Corps.
• noun One who holds this title.
• noun Chiefly British A noncommissioned or warrant officer of the highest rank in a company or unit of battalion size.
• noun A damselfish (Abudefduf saxatilis) of warm seas, having a flattened body with dark vertical stripes.

from The Century Dictionary.

• noun In the army, the highest non-commissioned officer in a regiment. He acts as assistant to the adjutant.
• noun The cow-pilot, a fish.

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

• noun Canada A senior non-commissioned appointment in the Army of a company or unit, directly responsible to the officer in charge for their soliders' performance, standards, discipline, morale, welfare, et al, that can be held by a Warrant Officer or above.
• noun US The most senior rank of non-commissioned officer in the United States Army and United States Marine Corps, ranking above a first sergeant.
• noun UK An appointment (not a rank) in the British Army and Royal Marines, denoting the most senior non-commissioned officer in a battalion, regiment or company.

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

• noun large blue-grey black-striped damselfish; nearly worldwide
• noun a noncommissioned officer serving as chief administrative officer of a headquarters unit of the Army