Source : Webster's Revised Unabridged Dictionary (1913)

Drum major \Drum" ma"jor\
   .

   1. The chief or first drummer of a regiment; an instructor of
      drummers.

   2. The marching leader of a military band. [U.S.]

   3. A noisy gathering. [R.] See under {Drum}, n., 4.

Source : WordNet®

drum major
     n : the leader of a marching band or drum corps