out-of-doors vs outdoors

out-of-doors and outdoors both are nouns.

Word	Noun	Adjective	Verb	Adverb
out-of-doors	Yes	No	No	No
outdoors	Yes	No	No	Yes

As nouns, out-of-doors and outdoors are synonyms defined as:

Other synonyms of out-of-doors include open, open air.

out-of-doors (noun)	outdoors (noun)
where the air is unconfined	where the air is unconfined

out-of-doors (adverb)	outdoors (adverb)
	outside a building