1. n. [Geophysics]

An implosion produced by locally low pressure, such as the collapse of a gas bubble in liquid (the energy of which is used as the source of seismic energy from air guns).

See: air gun,  bubble effect,  water gun

2. n. [Production]

The rapid formation and collapse of vapor pockets in a flowing liquid in localized regions of very low pressure. It is often a cause of erosive damage to pumps, throttling type valves and the piping itself. It can cause excessive noise.