(of a gun, cannon, Bunsen burner, etc.) To fire in the opposite direction, for example due to an obstruction in the barrel.

(of an engine) To experience a premature ignition of fuel or an ignition of exhaust gases, making a popping sound.

To fail in a manner that brings down further misfortune.

"His attempt to make money by importing luxury cars backfired horribly when fuel prices tripled."

A failure that leads to further misfortune.