an enlisted person of any of various grades in the armed forces, as, in the U.S. Army, from corporal to sergeant major inclusive
See noncommissioned officer in American Heritage Dictionary 4
(nŏnˌkə-mĭshˈənd)
noun Abbr. NCO
An enlisted member of the armed forces, such as a corporal, sergeant, or petty officer, appointed to a rank conferring leadership over other enlisted personnel.