- noting or pertaining to a speed less than that of sound in air at the same height above sea level.
Origin of subsonic
1940–45; sub- + -sonic
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for subsonic
- being, having, or travelling at a velocity below that of sounda subsonic aircraft
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.