safety valve

noun

1. a device that, when actuated by a gas or vapor pressure above a predetermined level, opens and allows the gas or vapor to escape until its pressure is reduced to a pressure equal to or below that of the predetermined level.Compare relief valve.
2. a harmless outlet for emotion, tension, etc.

noun

1. a valve in a pressure vessel that allows fluid to escape when a predetermined level of pressure has been reached
2. a harmless outlet for emotion, energy, tension, etc