What does fireproof mean?
Fireproof describes materials, objects, or structures that resist damage or destruction by fire. A fireproof safe protects documents from burning; fireproof doors and insulation slow the spread of flames through a building. The word also functions as a verb: builders and manufacturers fireproof materials by applying coatings, using noncombustible components, or designing structures that withstand extreme heat. Figuratively, English speakers call a plan, contract, or reputation fireproof when it seems incapable of failing or being damaged. In strict technical usage, however, nothing is perfectly fireproof — prolonged exposure to intense heat eventually degrades almost any substance — so engineers and safety professionals often prefer the more measured term fire-resistant. The word pairs the ancient concept of fire with 'proof', meaning protected against, reflecting centuries of human effort to guard homes, valuables, and lives from combustion. It remains an essential term in construction, insurance, law, and everyday speech about safety.
Resistant to fire; not readily damaged or destroyed by flames or intense heat.
"The theatre curtains were made of fireproof fabric."
Often used loosely for highly fire-resistant materials; technical contexts may prefer 'fire-resistant'.
To treat or construct something so that it is resistant to fire.
"They fireproofed the steel beams with intumescent coating."
Commonly used in construction and safety contexts; inflected forms include fireproofed and fireproofing.
Nothing is truly fireproof — engineers prefer 'fire-resistant' because given enough heat and time, everything gives in.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fireproof
Fireproof is a compound formed from 'fire', from Old English fȳr, and 'proof', from Old French preve/profe and ultimately Latin probare, meaning to test or prove. The '-proof' suffix denotes resistance or immunity to whatever precedes it, as in waterproof and rustproof. The compound arose in English around the early seventeenth century as builders and alchemists sought materials able to withstand flame. Its '-proof' construction links it to a whole family of protective compounds sharing the same Latin root.
Related word forms
How fireproof is actually used
Strictly speaking, few materials are entirely fireproof; technical and safety contexts often favour 'fire-resistant' or 'fire-retardant' as more accurate terms. The figurative sense ('a fireproof career') is informal but common.
Easily confused with fireproof
Fireproof implies near-total resistance to fire, whereas fire-retardant means merely slowed or hindered in burning.
A firewall is a barrier built to stop the spread of fire (or, figuratively, a digital security barrier), not a property of resisting fire.