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Meaning of safety valve

safe'ty valve"

Pronunciation: [key]
  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. Cf.
  2. a harmless outlet for emotion, tension, etc.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.