Supersonic
Supersonic means moving faster than the speed of sound, as opposed to subsonic. When an object travels supersonically, it overtakes its own sound waves, causing them to pile up and create a sonic boom.
The speed of sound varies depending on whether the sound wave is in air or another substance, and in air it depends on the temperature (increasing as the square root of the absolute temperature). However, in air in normal conditions it is about 760 miles per hour.
Probably the first man-made object to be supersonic was the tip of a whip; the crack of a whip is a sonic boom.
The speed of sound is often referred to as Mach 1, twice the speed as Mach 2 and so on. The name comes from the physicist Ernst Mach.