safety valve

American  

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.

2. a harmless outlet for emotion, tension, etc.

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safety valve British  

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

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Etymology

Origin of safety valve

First recorded in 1805–15

Example Sentences

The notwithstanding clause was brought in as a safety valve.

From BBC

It is an essential safety valve that remains "effective only if the conflict doesn't last too long", cautioned Perrin.

From Barron's

They happen when water treatment works become overwhelmed, usually after rainfall, allowing highly diluted sewage to spill into a river as a "safety valve".

From BBC

Dot plots and macro projections serve as a pressure safety valve where disagreement can be hashed out, without harming the consistency of the policy message.

From Barron's

The safety valves are drained, reserves are lower — and your money-market fund is the first domino.

From MarketWatch