sub·​son·​ic ˌsəb-ˈsä-nik How to pronounce subsonic (audio)
: of, relating to, or being a speed less than that of sound in air
: moving, capable of moving, or utilizing air currents moving at a subsonic speed
subsonically adverb

Example Sentences

Recent Examples on the Web Four groups—based at MIT, Boeing, GE, and Northrup Grumman—tackled NASA’s challenge to improve subsonic flight, in which the agency asked for aircraft designs that burn 70 percent less fuel and create less noise than existing planes. Emily Elert, Discover Magazine, 28 Dec. 2010 At subsonic speeds, the jet maintained a classic straight-wing profile, providing impressive maneuverability. Stephen Witt, Popular Mechanics, 2 Mar. 2023 Aardvark, had wings with variable geometry, which would stay fully open at subsonic speeds, and then pivot closer to the fuselage when flying supersonic, offering the best possible handling and fuel efficiency. Jacopo Prisco, CNN, 27 Jan. 2023 The XQ-58A Valkyrie demonstrator, a long-range, high subsonic unmanned air vehicle completed its inaugural flight March 5, 2019 at Yuma Proving Grounds, Arizona. IEEE Spectrum, 23 Jan. 2023 It was first proposed in 2010, and in 2017, NASA awarded a contract for research into the design for its new subsonic X-plane. Jennifer Walter, Discover Magazine, 15 Oct. 2022 Voyager 1 crossed another border, the termination shock, where the solar wind abruptly slows to subsonic speed, back in 2004. Michael E. Bakich, Discover Magazine, 29 Oct. 2019 Project 80 is supposedly a subsonic flying wing with an unrefueled range of 9,300 miles, enough to deliver nuclear bombs on targets in North America. Kyle Mizokami, Popular Mechanics, 1 Nov. 2022 After studying publicly available information on the U.S. arsenal, the Ukrainians concluded that the Pentagon had a surplus of A-10s, the aging, subsonic attack aircraft known as Thunderbolts. Isabelle Khurshudyan, Washington Post, 23 Dec. 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'subsonic.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


International Scientific Vocabulary

First Known Use

1920, in the meaning defined at sense 3

Time Traveler
The first known use of subsonic was in 1920

Dictionary Entries Near subsonic

Cite this Entry

“Subsonic.” Dictionary, Merriam-Webster, Accessed 23 Mar. 2023.

Kids Definition


sub·​son·​ic ˌsəb-ˈsän-ik How to pronounce subsonic (audio)
: of, relating to, or being a speed less than that of sound in air
: moving, capable of moving, or using air currents moving at a subsonic speed
Last Updated: - Updated example sentences
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