What is the X in X-mas?
supersonic su·per·son·ic (sōō'pər-sŏn'ĭk)
Having, caused by, or relating to a speed greater than the speed of sound in a given medium, especially air.
Of or relating to sound waves beyond human audibility.
Having a speed greater than that of sound in a designated medium, usually air; having a speed greater than Mach 1. Compare hypersonic, subsonic, transonic.