Subsonic

adj, noun

adj, noun ·Rare ·Advanced level

Definitions

Noun
  1. 1
    an aircraft whose maximum speed is less than the speed of sound
Adjective
  1. 1
    having a frequency too low to be audible not-comparable
  2. 2
    very quiet, almost inaudible literary, not-comparable

    "The noise of the ship was all around her. The faint subsonic rumble of the reactor and drive. (Leviathan Wakes, James S. A. Corey)"

  3. 3
    (aviation) less than the speed of sound (in the same medium, and at the same temperature and pressure) not-comparable

    "But British Airways Flight 112 made the trek in under five hours, setting a new record for the fastest subsonic commercial flight across the Atlantic Ocean."

  4. 4
    with a Mach number such that 0.3 < Ma < 0.8 (approximately - the exact limits vary between sources) not-comparable
Adjective
  1. 1
    (of speed) less than that of sound in a designated medium wordnet

Synonyms

All synonyms
acousticacousticalphonictransonic

Example

More examples

"The noise of the ship was all around her. The faint subsonic rumble of the reactor and drive. (Leviathan Wakes, James S. A. Corey)"

Etymology

From sub- + sonic.

Related phrases

mach numberspeed of sound

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.