safety valven.1. A valve in a pressure container, as in a steam boiler, that automatically opens when pressure reaches a dangerous level.2. An outlet for the release of repressed energy or emotion.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.safety valve n 1. (Mechanical Engineering) 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 Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014safe?ty valve` n. 1. a device that opens to release a fluid before pressure reaches dangerous levels. 2. a harmless outlet for pent-up feelings. [1805?15] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.