subsonic

[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.
Origin
1940-45; sub- + -sonic
Related forms
subsonically, adverb
Examples from the web for subsonic
  • Flight engineers define three categories of speed: subsonic, supersonic, and hypersonic.
  • So the region where the flow changes from subsonic to supersonic is an event horizon.
  • Also, supersonic speeds produce shock that is not a part of subsonic velocities.
British Dictionary definitions for subsonic

subsonic

/sʌbˈsɒnɪk/
adjective
1.
being, having, or travelling at a velocity below that of sound: a subsonic aircraft
subsonic in Science
subsonic
(sŭb-sŏn'ĭk)
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.