blowback

/ (ˈbləʊˌbæk) /

noun

the escape to the rear of gases formed during the firing of a weapon or in a boiler, internal-combustion engine, etc
the action of a light automatic weapon in which the expanding gases of the propellant force back the bolt, thus reloading the weapon
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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