bush vs outback

bush and outback both are nouns.

Word	Noun	Adjective	Verb	Adverb
bush	Yes	Yes	Yes	No
outback	Yes	Yes	No	No

As nouns, outback is a hyponym of bush; that is, outback is a word with a more specific, narrower meaning than bush:

bush (noun)	outback (noun)
hair growing in the pubic area	the bush country of the interior of Australia
dense vegetation consisting of stunted trees or bushes
a large wilderness area
a low woody perennial plant usually having several major stems

bush (adjective)	outback (adjective)
not of the highest quality or sophistication	inaccessible and sparsely populated

bush (verb)	outback (verb)
provide with a bushing