1. moving at a speed less than the speed of sound
Usage: physics; aviation
2. relating to or involving speeds below the speed of sound
Usage: technical

Examples

• The subsonic aircraft flew quietly overhead.
• Most commercial airliners operate at subsonic speeds.
• The bullet traveled at subsonic velocity through the air.
• Engineers tested the subsonic wind tunnel design.
• The jet’s subsonic flight was much quieter than expected.
• Subsonic ammunition produces less noise when fired.