The Collaborative International Dictionary of English v.0.48:
Drum major \Drum" ma"jor\ . 1. The chief or first drummer of a regiment; an instructor of drummers. [1913 Webster] 2. The marching leader of a military band. [U.S.] [1913 Webster] 3. A noisy gathering. [R.] See under Drum, n., 4. [1913 Webster]WordNet (r) 3.0 (2006):
drum major n 1: the leader of a marching band or drum corps