What does combust mean?
To combust is to catch fire and burn, undergoing the chemical process of combustion in which a substance reacts rapidly with oxygen and releases heat and light. The verb is most at home in technical and scientific writing, describing fuels, gases, and materials that ignite under particular conditions, as when hydrogen combusts on contact with a flame. Outside the laboratory it also serves figuratively, often humorously, to describe a person who suddenly erupts in anger or excitement — someone might be said to have spontaneously combusted upon hearing outrageous news. Derived forms such as "combustion," "combustible," and "noncombustible" are far more frequent than the bare verb itself. Because everyday speech tends toward simpler phrasing like "catch fire" or "burn up," using "combust" lends a sentence precision and a slightly formal, scientific flavor, making it a useful word for anyone writing about chemistry, safety, or vividly dramatic reactions.
To catch fire and burn; to undergo combustion.
"The methane will combust if exposed to an open flame."
Standard use is intransitive; transitive uses are largely confined to industrial jargon.
To erupt suddenly in anger, excitement, or other intense emotion.
"He nearly combusted when he saw the final bill."
Before it meant anything about fire, "combust" carried a whiff of alchemy — early chemists used it for substances that burned away entirely.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of combust
Combust derives from the Latin verb comburere (past participle combustus), meaning "to burn up completely," formed from com- (an intensive prefix) and urere ("to burn"). The word entered English in the early modern period, initially in learned and alchemical contexts before settling into general scientific usage. It shares its Latin root with related English borrowings built on the same stem, notably combustion and combustible.
Related word forms
How combust is actually used
Primarily formal or technical register; everyday speech usually prefers "catch fire" or "burst into flames." The figurative sense, often in phrases like "spontaneously combusted," is common informally and frequently hyperbolic. Intransitive in standard use; the passive "was combusted" is rare outside industrial contexts.
Easily confused with combust
"Consume" means to eat, use up, or destroy something broadly, while "combust" specifically means to catch fire and burn.