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Definition of Subsonic
1. Adjective. (of speed) less than that of sound in a designated medium. "Aircraft flying at subsonic speeds" 
Definition of Subsonic
1. moving at a speed less than that of sound [adj]
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1. Adjective. (of speed) less than that of sound in a designated medium. "Aircraft flying at subsonic speeds" 
1. moving at a speed less than that of sound [adj]