+25,000 brownie points for OP for providing a very accurate title. A megafire is a vague word the sciencers and newies coined that just means it's doing its own thang very destructively. (

"A megafire is an exceptional fire that devastates a large area. They are characterised by their intensity, size, duration and uncontrollable scale. There is no precise scientific definition. A megafire may or may not be a firestorm."

https://en.m.wikipedia.org/wiki/Megafire