- To catch fire; burst into flame: The fire started when a pile of oily rags spontaneously combusted.
- To undergo combustion; burn: As the fuels were combusting they gave off noxious vapors.
- To become suddenly angry or agitated: The defendant combusted when he heard the verdict.
- To cause to burn; ignite.
- To cause to become angry or violent: riots that are combusting whole provinces.