What is Sonic Boom?

Legal Definition
A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion. The crack of a supersonic bullet passing overhead or the crack of a bullwhip are examples of a sonic boom in miniature.
-- Wikipedia
Legal Definition
The shock waves heard and felt when an aircarft of any sort travels at the speed of sound.