# subsonic

> English word · Adjective · frequency rank #52,027

## Definitions
1. having a frequency too low to be audible
2. very quiet, almost inaudible
3. (aviation) less than the speed of sound (in the same medium, and at the same temperature and pressure)
4. with a Mach number such that 0.3 < Ma < 0.8 (approximately - the exact limits vary between sources)

## Etymology
From sub- + sonic.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/subsonic