[ suhb-son-ik ]
/ sʌbˈsɒn ɪk /


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


sub·son·i·cal·ly, adverb Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for subsonic

  • And its booming notes descended to subsonic throbbings that gripped and wrung the nerves to anguish.

    The Record of Currupira|Robert Abernathy
  • Most of their conversation is carried on in tones of subsonic frequency, so your ears cannot hear it.

    The Asses of Balaam|Gordon Randall Garrett

British Dictionary definitions for subsonic

/ (sʌbˈsɒnɪk) /


being, having, or travelling at a velocity below that of sounda subsonic aircraft
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Science definitions for subsonic

[ sŭb-sŏnĭk ]

Having a speed less than that of sound in a designated medium, usually air; having a velocity less than Mach 1. Compare hypersonic supersonic transonic.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.