Adjective
(of a speed, aviation) Equal to, or greater than, or capable of achieving, five times the speed of sound.
(of a speed, aeronautics) Far enough above the speed of sound as to cause significant differences in behaviour due to chemical reactions or dissociation of the air.
Source: en.wiktionary.orgA fourth classification, hypersonic flow, refers to flows where the flow speed is much greater than the speed of sound. Source: Internet
Already, the forces of Russia, China, and Iran are conducting joint naval drills, Russian and American forces have already brawled with each other in Syria, and Russia has announced a key breakthrough in hypersonic weapons technology. Source: Internet
Aerodynamicists disagree on the precise definition of hypersonic flow. Source: Internet
Air-breathing designs typically fly at supersonic or hypersonic speeds, and usually include a rocket engine for the final burn for orbit. Source: Internet
Clearly Boeing is betting big on hypersonic P2P and they're in a better position to capitalize on it with significantly fewer risks of reaching that point. Source: Internet
But it is still a Cold War subsonic cruise missile that seems a bit of a dinosaur when compared to the supersonic and hypersonic weapons that are being developed today. Source: Internet