noun

1. ☆ a fire started to stop an advancing prairie fire or forest fire by creating a burned area in its path
2. a premature ignition of fuel or an explosion of unburned exhaust gases in an internal-combustion engine, sometimes preventing the completion of the compression stroke and reversing the direction of the piston
3. an explosive force toward the breech, rather than through the muzzle, of a firearm

intransitive verb backfired -·fired′, backfiring -·fir′·ing

1. ☆ to use or set a backfire
2. to explode as a backfire
3. to have an unexpected and unwelcome result; go awry; boomerang his plan backfired