black out vs blackout

black out is not a noun while blackout is a noun.

Word	Noun	Adjective	Verb	Adverb
black out	No	No	Yes	No
blackout	Yes	No	No	No

black out (noun)	blackout (noun)
	a momentary loss of consciousness
	partial or total loss of memory
	the failure of electric power for a general region
	darkness resulting from the extinction of lights (as in a city invisible to enemy aircraft)
	a suspension of radio or tv broadcasting

black out (verb)	blackout (verb)
lose consciousness due to a sudden trauma, for example
suppress by censorship as for political reasons
darken completely