1. A loud noise made by the explosion of fuel in the manifold or exhaust of an internal combustion engine.
2. A miscalculation that recoils on its maker; SYN. boomerang.

1. To emit a loud noise as a result of undergoing a backfire, as of cars.
2. To have an unexpected and undesired effect; SYN. backlash.
3. To set a controlled fire to halt an advancing forest to prairie fire. back-fire.