subsonic
Americanadjective
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noting or pertaining to a speed less than that of sound in air at the same height above sea level.
adjective
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Having a speed less than that of sound in a designated medium, usually air; having a velocity less than Mach 1.
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Compare hypersonic supersonic transonic
Other Word Forms
Etymology
Origin of subsonic
1940–45; sub- + sonic ( def. )
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
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
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
They presented records showing that Peterson, who lived in Durham, N.C., bought silencer components online and researched subsonic ammunition, which is quieter than standard rounds.
From Los Angeles Times ● Dec. 5, 2023
The horse didn’t seem happy about it, but he slowed to subsonic as they zipped through the city streets.
From "The Son of Neptune" by Rick Riordan
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
