Back fire. (a) A fire started ahead of a forest or prairie fire to burn only against the wind, so that when the two fires meet both must go out for lack of fuel. (b) A premature explosion in the cylinder of a gas or oil engine during the exhaust or the compression stroke, tending to drive the piston in a direction reverse to that in which it should travel; also, an explosion in the exhaust passages of such ah engine.

Back fire. (a) A fire started ahead of a forest or prairie fire to burn only against the wind, so that when the two fires meet both must go out for lack of fuel. (b) A premature explosion in the cylinder of a gas or oil engine during the exhaust or the compression stroke, tending to drive the piston in a direction reverse to that in which it should travel; also, an explosion in the exhaust passages of such ah engine.

• (of a gun or cannon) to fire in the opposite direction, for example due to an obstruction in the barrel
  
• to fail in a manner that brings down further misfortune.
       His attempt to make money by importing luxury cars horribly backfired when fuel prices tripled.