1. 1. (Abbr. MSG) A noncommissioned rank in the U.S. Army that is above sergeant first class and below the position of sergeant major.
   2. (Abbr. MSgt) A noncommissioned rank in the U.S. Air Force that is above technical sergeant and below senior master sergeant.
   3. (Abbr. MSGT) A noncommissioned rank in the U.S. Marine Corps that is above gunnery sergeant and below the position of sergeant major.
2. One who holds the rank of master sergeant.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.