drum major

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A person who leads a marching band or drum corps, often twirling a baton.

from The Century Dictionary.

• noun The chief or first drummer of a regiment.
• noun One who directs the evolutions of a band or drum-corps in marching.
• noun A riotous evening assembly. See drum, 9.

from the GNU version of the Collaborative International Dictionary of English.

• The chief or first drummer of a regiment; an instructor of drummers.
• U.S. The marching leader of a military band.
• A noisy gathering. [R.] See under Drum, n., 4.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One who conducts and commands a marching band.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the leader of a marching band or drum corps