Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


adjective sub·son·ic \ˌsəb-ˈsä-nik\

Simple Definition of subsonic

  • : slower than the speed of sound

Source: Merriam-Webster's Learner's Dictionary

Full Definition of subsonic

  1. 1 :  of, relating to, or being a speed less than that of sound in air

  2. 2 :  moving, capable of moving, or utilizing air currents moving at a subsonic speed

  3. 3 :  infrasonic 1


play \-ni-k(ə-)lē\ adverb

Origin and Etymology of subsonic

International Scientific Vocabulary

First Known Use: 1937

Seen and Heard

What made you want to look up subsonic? Please tell us where you read or heard it (including the quote, if possible).