1
: an act or instance of burning
Smoke is produced during combustion.
2
: a usually rapid chemical process (such as oxidation) that produces heat and usually light
The carburetor mixes fuel with air for combustion.
also : a slower oxidation (as in the body)
3
: violent agitation : tumult
… periods of great social combustion alternating with quiescence …—Kurt Andersen

Examples of combustion in a Sentence

Combustion may occur at high temperatures. This ratio of air to fuel results in better combustion.
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Coal combustion leaves behind fly ash, a fine mineral residue that companies dumped in landfills or stored in enormous ash ponds. — Edward D. Melillo, The Conversation, 30 Sep. 2026 Möhring explained that this showed the team that very clean combustion was possible in the lab. — Georgina Jedikovska, Interesting Engineering, 28 Sep. 2026 The company says the aircraft could cut flight-training costs by as much as 80% compared to conventional combustion-engine trainers – a number worth watching closely, given how badly the industry needs cheaper ways to churn out new pilots. — New Atlas, 25 Sep. 2026 Carbon monoxide released by combustion reduces the amount of oxygen that the blood can carry. — Katia Hetter, CNN Money, 16 Sep. 2026 See All Example Sentences for combustion

Word History

Etymology

Middle English combustioun "burning, calcination," borrowed from Anglo-French & Late Latin; Anglo-French combustion, borrowed from Late Latin combustiōn-, combustiō "burning up (of the dead or by the fires in hell)," from Latin combus-, variant stem of combūrere "to destroy with fire, reduce to ashes" + -tiōn-, tiō, suffix of verbal action — more at combust

First Known Use

15th century, in the meaning defined at sense 1

Time Traveler
The first known use of combustion was in the 15th century

Cite this Entry

“Combustion.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/combustion. Accessed 9 Oct. 2026.

Kids Definition

combustion

noun
1
: an act or instance of burning
2
: a chemical process in which substances combine with oxygen

Medical Definition

combustion

noun
: a usually very rapid chemical process (as oxidation) that produces heat and usually light
also : a slower oxidation (as in the body)

More from Merriam-Webster on combustion

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!