subsonic

American  

[suhb-son-ik] / sʌbˈsɒn ɪk /

adjective

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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subsonic British  

/ sʌbˈsɒnɪk /

adjective

1. being, having, or travelling at a velocity below that of sound

   a subsonic aircraft

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subsonic Scientific  

/ sŭb-sŏn′ĭk /

1. Having a speed less than that of sound in a designated medium, usually air; having a velocity less than Mach 1.

2. Compare hypersonic supersonic transonic

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Other Word Forms

• subsonically
  adverb

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Etymology

Origin of subsonic

1940–45; sub- + sonic ( def. )

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Compare meaning

How does subsonic compare to similar and commonly confused words? Explore the most common comparisons:

• subsonic vs. supersonic

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Example Sentences

See Examples For:

subsonic

Engineers will continue conducting a mix of subsonic and lower-altitude flights to monitor the aircraft's behavior under a variety of conditions.

From Science Daily ● Jun. 1, 2026

Lumbering up ahead was an Iranian air force Yak-130, a Russian-made subsonic jet trainer developed in the early 1990s and first flown almost 30 years ago.

From The Wall Street Journal ● Mar. 6, 2026

Right above the shores of Huntington Beach, a retired American subsonic T-33 fighter jet darted across the blue canvas of a clear afternoon sky, leaving a spiraling plume of smoke in its wake.

From Los Angeles Times ● Oct. 4, 2025

In terms of purely destructive power, however, hypersonic missiles are not hugely different from supersonic or subsonic cruise missiles, according to Mr Freer.

From BBC ● Aug. 21, 2025

Modeling flight at transonic speeds was a particularly knotty problem, because of the subsonic and supersonic winds that passed over the plane or model simultaneously.

From "Hidden Figures" by Margot Lee Shetterly

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