flashover

Deverbal from flash over.

flashover (countable and uncountable, plural flashovers)

1. The near simultaneous ignition of all combustible material in an enclosed area.
   • 2026 January 1, Chris Michael, Rory Carroll, “‘It happened in seconds’: sudden inferno brings horror to Swiss ski resort”, in The Guardian‎^[1], →ISSN:

     The blaze turned into what Swiss officials called an embrasement généralisé, a term for a fire that releases combustible gases that can ignite violently, triggering what English-speaking firefighters call a flashover or backdraft.

2. An unintended electric discharge or arc over or around an insulator.

   Synonym: sparkover

   • 1960 April, “Talking of Trains: Safety with 25kV a.c.”, in Trains Illustrated, page 203:

     The overhead line was energised at 25,000 volts and the height of the contact wire was reduced to 11 in. above the chimney, then to 5 and finally to 2 in.; at this last, short distance the flashover occurred, but all the men were perfectly safe because the current went direct to earth through the locomotive.

• flashover voltage