wildfire

What it means

1. countableuncountableA rapidly spreading fire, especially one occurring in a wildland area.

   Synonyms: forest fire

2. countablehistoricaluncountableGreek fire.
3. countableuncountabledermatologyA spreading disease of the skin, particularly erysipelas.

In a sentence

So, it appears a revolution has happened and a very unexpected one. Of course it was only a matter of time before it happened. With WiFi connectivity spreading faster than wildfire and a laptop or tablet in one’s bag, what’s the point of a mobile nowadays?

2015 January 18, Monty Munford, “What’s the point of carrying a mobile phone nowadays?”, in The Daily Telegraph

Where it comes from

1. Old Englishwilde fȳr
2. Middle Englishwilde fyr
3. Englishwildfire

Inherited from Middle English wilde fyr, wilde fire, wylde fyre, from Old English wilde fȳr. By surface analysis, wild + fire.