Blowback is the third episode of the fifth season. It was released on 17 October 2008.
1. the escape to the rear of gases formed during the firing of a weapon or in a boiler, internal-combustion engine, etc.
2. the action of a light automatic weapon in which the expanding gases of the propellant force back the bolt, thus reloading the weapon
Here the word conveys a sense of the ramifications and lingering consequences of a course of action, and perhaps the risk to others caught in the blast.