flare-up vs flare up

flare-up is a noun but flare up is not a noun.

Word	Noun	Adjective	Verb	Adverb
flare-up	Yes	No	No	No
flare up	No	No	Yes	No

flare-up (noun)	flare up (noun)
a sudden intense happening

flare-up (verb)	flare up (verb)
	erupt or intensify suddenly
	ignite quickly and suddenly, especially after having died down