Questions about example sentences with, and the definition and usage of "Combust"

A: Spontaneous = Instantly
Combustion = Catch fire

Spontaneous combustion is a rare phenomenon where someone bursts into flames, with no seeming cause for it.

A: Hmm.
Combusting means consumed by fire.
With that you know she's basically saying she's,
Erupting into tears
Bursting into tears
Falling to tears
Suddenly crying
Came quickly to tears
Etc...

Combust literally means consumed by fire though. I guess you can say you combust as in quickly or rapidly became something.
Combusting into anger.
Combusting into tears.
Combusting into sadness.
Combusting into despair.
Combusting into hatred.
Like an emotion.

I combusted into anger.
I'm going to combust into tears.
I'm combusting into sadness.
I may combust into despair.
He made me combust into hatred.

A: coal is a combustible material. Be careful with that canister, it contains a highly combustible gas. Airlines never use combustible materials in passenger seats. The bonfire is burning nicely. Be careful you don’t burn yourself using that barbecue. You didn’t use any sunscreen, so you got burnt. The lorry burst into flames and is now completely ablaze. They sat around the blazing fire singing songs into the night.

A: Combust is the very beginning stage of burning/fire. It is often used as combustible. This form describes a material that can easily catch fire or combust.