combust vs flame

combust is not a noun while flame is a noun.

Word	Noun	Adjective	Verb	Adverb
combust	No	No	Yes	No
flame	Yes	No	Yes	No

As verbs, flame is a hyponym of combust; that is, flame is a word with a more specific, narrower meaning than combust:

combust (noun)	flame (noun)
	the process of combustion of inflammable materials producing heat and light and (often) smoke

combust (verb)	flame (verb)
undergo combustion	criticize harshly, usually via an electronic medium
get very angry and fly into a rage	be in flames or aflame
cause to become violent or angry	shine with a sudden light
start to burn or burst into flames
cause to burn or combust