walkout vs walk out

walkout is a noun but walk out is not a noun.

Word	Noun	Adjective	Verb	Adverb
walkout	Yes	No	No	No
walk out	No	No	Yes	No

walkout (noun)	walk out (noun)
a strike in which the workers walk out
the act of walking out (of a meeting or organization) as a sign of protest

walkout (verb)	walk out (verb)
	leave suddenly, often as an expression of disapproval
	leave abruptly, often in protest or anger
	stop work in order to press demands