backfire

UK: /ˌbækˈfaɪə^r/ US: /ˈbækˌfaɪr/ ,(bak′fī^ər′)

Inflections of 'backfire' (v): (⇒ conjugate)

backfires

v 3rd person singular

backfiring

v pres p

backfired

v past

backfired

v past p

WordReference Random House Learner's Dictionary of American English © 2026

back•fire /ˈbækˌfaɪr/   v., -fired, -fir•ing, n. 
v. [no obj]

1. Automotive (of a car engine) to have a loud explosion that occurs too soon for proper combustion.
2. to have a result opposite to that expected;
   go wrong.

n. [countable]

3. Automotive (in a car engine) an explosive igniting of fuel that occurs too soon for proper combustion.

WordReference Random House Unabridged Dictionary of American English © 2026

back•fire  (bak′fī^ər′), v., -fired, -fir•ing, n. 
v.i. 

1. Automotive (of an internal-combustion engine) to have a loud, premature explosion in the intake manifold.
2. to bring a result opposite to that which was planned or expected:
   The plot backfired.
3. to start a fire deliberately in order to check a forest or prairie fire by creating a barren area in advance of it.

n. 

4. Automotive (in an internal-combustion engine) premature ignition of fuel in the intake manifold.
5. an explosion coming out of the breech of a firearm.
6. a fire started intentionally to check the advance of a forest or prairie fire.

• back² + fire 1775–85, American.

Synonyms

• 2. miscarry, boomerang; flop, bomb, wash out.

Collins Concise English Dictionary © HarperCollins Publishers::

backfire / ˌbækˈfaɪə/ verb (intransitive)

1. (of an internal-combustion engine) to emit a loud noise as a result of an explosion in the inlet manifold or exhaust system
2. to start a controlled fire in order to halt an advancing forest or prairie fire by creating a barren area

noun

1. (in an internal-combustion engine) an explosion of unburnt gases in the exhaust system
2. a controlled fire started to create a barren area that will halt an advancing forest or prairie fire