Source : Webster's Revised Unabridged Dictionary (1913)

'Etat Major \['E]`tat" Ma`jor"\ [F., fr. ['e]tat state + L.
   major greater.] (Mil.)
   The staff of an army, including all officers above the rank
   of colonel, also, all adjutants, inspectors, quartermasters,
   commissaries, engineers, ordnance officers, paymasters,
   physicians, signal officers, judge advocates; also, the
   noncommissioned assistants of the above officers.