Blowback

Noun

 * 1) A type of action where the pressure from the fired cartridge blows a sliding mechanism backward to extract the fired cartridge, chamber another cartridge, and cock the hammer.
 * 2) An unintended adverse result, especially of a political action.
 * 3) (military) Escape, to the rear and under pressure, of gases formed during the firing of the weapon.
 * 4) (military) Type of weapon operation in which the force of expanding gases acting to the rear against the face of the bolt furnishes all the energy required to initiate the complete cycle of operation.  A weapon which employs this method of operation is characterized by the absence of any breech-lock or bolt-lock mechanism.
 * 5) * Blowback may be caused by a defective breech mechanism, a ruptured cartridge case, or a faulty primer.
 * 6)  The act of shotgunning (inhaling from a pipe etc. and exhaling into another smoker's mouth).