first sergeant definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
U.S. Army, U.S. Marine Corps the noncommissioned officer, usually a master sergeant, serving as chief administrative assistant to the commander of a company, battery, etc.
first sergeant definition by American Heritage Dictionary
The senior noncommissioned officer of a U.S. Army or Marine Corps unit, who is equivalent in rank to a master sergeant and performs administrative duties.