Definition of: combustion

(kəm·bus′chən) noun
1. The action or operation of burning; the state of being on fire.
2. Chem. The combination of a substance with oxygen, accompanied by the generation of heat and sometimes light.
3. Physiol. Oxidation, as of fuel, or of food in the body.
4. Disturbance; tumult. See synonyms under FIRE. [<LL combustio, -onis <comburere burn up]
—com·bus′tive adjective