Definition of "safety valve" []

• A valve in a pressure container, as in a steam boiler, that automatically opens when pressure reaches a dangerous level. (noun)
• An outlet for the release of repressed energy or emotion. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The characteristic mental state is one of doubt, of indecision, of inadequacy, of restlessness, of tension, of discomfort and of dissatisfaction, which is more or less unappeasable and irrepressible and uncontrollable until it finds vent in a rather explosive series of motor expressions which, as it were, are the safety valve for the peculiar feeling of tension and discomfort which the individual has been experiencing and which is accompanied by a sense of relief, satisfaction and a relative degree of comfort and mental rest."
• "The Papagos pursue a course which is certainly peculiar to them, of producing a more steady and, perhaps, not too violent traction upon the cord, by so attaching it that the amount of force to be used is left to the judgment and the sensations of the patient; it seems as if her sense of pain were to serve as a safety valve for the amount of force to be expended, and thus the proper limit determined and dangerous consequences avoided."