Wiktionary
n. The propagation of a flame away from its source of ignition.
Wikipedia
Flame spread or surface burning characteristics rating is a ranking derived by laboratory standard test methodology of a material's propensity to burn rapidly and spread flames. There are several standardized methods of determining flame spread,
Usage examples of "flame spread".
The glow of its flame spread over the room softly and touched on the men's faces, proving them to be the same two who had huddled across the room from them at mealtime.
That's what it meant when the flame spread from the green to the yellow candle.
Fiery fingers of flame spread out from him, lighting the darkness, racing through the wet grass, dancing on top of the water as though it were covered with oil.
As they watched in amazement, the rigging caught fire and sheets of flame spread to the sails.
Two of the bottles hit the lead tank, and burst into flames, Flame spread across the vehicle, and rivers of fire ran off its sides and were dispersed by the ground effect fan.
I had seen the flame spread when it struck the surface, and now I realized that my hope had been vain.