v. 1. To say your name or count "One! Two! Three! Four!" as you march. Used as orders in U.S. military service. "Sound off!" said the sergeant, and the soldiers shouted, "One! Two! Three! Four!" with each step as they marched. 2. informal To tell what you know or think in a loud clear voice, especially to brag or complain. If you don't like the way we're doing the job, sound off! George sounded off about how the game should have been played. The teacher is always sounding off about the students not doing their homework.
Compare: SPEAK ONE'S PIECE, SPEAK OUT.