Shock Wave
Definition
A violent, abrupt pressure wave created when something moves faster than the speed of sound in the medium.
Technical definition
A propagating discontinuity in pressure, density, and temperature formed when a source exceeds the wave speed — wavefronts pile up into a single intense front. The ‘crack’ of a supersonic jet's sonic boom is a shock wave reaching the ground.
Example
A supersonic jet creates a cone-shaped shock wave; when it sweeps past you, you hear it as a sonic boom — a sudden jump in air pressure, not an explosion.
Common confusion
A sonic boom is not a one-time ‘bang’ when the jet breaks the sound barrier — it is continuous. The shock cone trails the aircraft the whole time it is supersonic; you hear the boom as the cone passes over you.