Old Testament vs burning bush

Old Testament and burning bush both are nouns.

Word	Noun	Adjective	Verb	Adverb
Old Testament	Yes	No	No	No
burning bush	Yes	No	No	No

Old Testament (noun)	burning bush (noun)
the collection of books comprising the sacred scripture of the Hebrews and recording their history as the chosen people; the first half of the Christian Bible	(Old Testament) the bush that burned without being consumed and from which God spoke to Moses
	densely branched Eurasian plant; foliage turns purple-red in autumn
	deciduous shrub having purple capsules enclosing scarlet seeds
	Eurasian perennial herb with white flowers that emit flammable vapor in hot weather