GNU Collaborative International Dictionary of English

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Found one definition

1.       
   hypersonic (?), n. [Pref. hyper- + sonic.] (Aeronautics) Pertaining to or moving at a speed greatly in excess of the speed of sound, usually meaning greater than mach 5.  All speeds in excess of the speed of sound are supersonic, but to be hypersonic requires even higher speed.
   
   [PJC]