from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Of, relating to, or capable of speed equal to or exceeding five times the speed of sound.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. equal to, or greater than, or capable of achieving, five times the speed of sound.
- adj. far enough above the speed of sound so as to cause significant differences in behaviour due to chemical reactions or disassociation of the air.
from the GNU version of the Collaborative International Dictionary of English
- n. 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.
hyper- + sonic (Wiktionary)