Combustion, n.
Etymology: [L. combustio: cf. F. combustion.]
1. The state of burning.
2. (Chem.)
The combination of a combustible with a supporter of combustion, producing heat, and sometimes both light and heat. Combustion results is common cases from the mutual chemical action and reaction of the combustible and the oxygen of the atmosphere, whereby a new compound is formed. Ure. Supporter of combustion (Chem.), a gas as oxygen, the combination of which with a combustible, as coal, constitutes combustion.
3. Violent agitation; confusion; tumult. [Obs.] There [were] great combustions and divisions among the heads of the university. Mede. But say from whence this new combustion springs. Dryden.
Shades of meaning
Fernald has no entry of its own for combustion; he lists it under fire.
Where he writes about it:
Combustion is the essential fact which is at the basis of that assemblage of visible phenomenon which we call fire; combustion being the continuous chemical combination of a substance with some element, as oxygen, evolving heat, and extending from slow processes, such as those by which the heat of the human body is maintained, to the processes producing the most intense light also, as in a blast-furnace, or on the surface of the sun. — from fire
Combustion is the scientific, fire the popular term. — from fire