What does demister mean?
A demister is a device — or occasionally a chemical treatment — designed to remove condensation, or 'mist', from glass surfaces. Its most familiar role is in cars: when warm, humid air inside the cabin meets a cold windscreen, water droplets form and obscure the driver's view, and switching on the demister directs dry, heated air across the glass until the moisture evaporates. Most vehicles include both a front windscreen demister and a rear-window version, typically an embedded electrical heating grid. Beyond motoring, demister products such as sprays and wipes are used on bathroom mirrors, goggles, and camera lenses to prevent fogging. The word is most prevalent in British English; American speakers tend to say 'defroster' or 'defogger' instead. Practical and unglamorous, the demister nonetheless solves one of driving's most persistent small hazards — sudden loss of visibility on a cold, damp morning — making it an essential piece of everyday vocabulary.
nounA device or substance that removes mist or condensation, especially from a vehicle windscreen or window.
- A device in a vehicle that blows warm air onto glass to clear condensation.
- A chemical agent applied to glass or mirrors to prevent misting.
"Switch on the demister to clear the windscreen before setting off."
"She flicked on the rear demister as the windows began to fog up."
"A dab of demister on the bathroom mirror keeps it clear after a hot shower."
Regular plural; used when referring to multiple units or to front and rear devices together.
"Both demisters were running full blast."
The humble demister is why your breath doesn't turn your windscreen into a fog bank every winter morning.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of demister
Demister derives from the verb 'demist', formed in the twentieth century from the prefix 'de-' (indicating removal) plus 'mist', a noun of Germanic origin dating back to Old English. The word arose with the spread of motor vehicles and their ventilation systems, particularly in Britain, where it became standard automotive terminology. It shares its root with 'mist' and its adjective 'misty', both long-established English words of common Germanic ancestry.
How demister is actually used
Most common in British English; American English more often uses 'defroster' or 'defogger' for the same feature. Neutral register, everyday automotive vocabulary.
Easily confused with demister
A defroster removes ice or frost by heating, while a demister clears condensation (mist) and the terms often overlap for the same car controls.