• synonyms


  1. noting or pertaining to a speed less than that of sound in air at the same height above sea level.
  2. infrasonic.
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Origin of subsonic

1940–45; sub- + -sonic
Related formssub·son·i·cal·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for subsonic

Historical Examples of 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


  1. being, having, or travelling at a velocity below that of sounda subsonic aircraft
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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

subsonic in Science


  1. 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.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.