What is "back fire"

backfire \backfire\, back fire \back fire\

1. 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.

2. 1. 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 called a knock or ping.

   2. an explosion in the exhaust passages of an internal combustion engine.

n. 1 a small, controlled fire set in the path of a larger uncontrolled fire, in order to limit the spread of the large fire by removing its fuel. 2 an explosion produced either by a running internal combustion engine that occurs in the air intake or exhaust system rather than inside the combustion chamber or unburned fuel or hydrocarbons ignited somewhere in the exhaust system.