Subsonic
ahd-5
adjective.
Of less than audible frequency.
adjective.
Having a speed less than that of sound in a designated medium.
Wiktionary, Creative Commons Attribution/Share-Alike License
adjective.
having a
frequency
too low to be
audible
adjective.
less than the
speed of sound
(in the same
medium
, and at the same
temperature
and
pressure
)
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adjective.
(of speed) less than that of sound in a designated medium