bring down vs overturn

bring down is not a noun while overturn is a noun.

Word	Noun	Adjective	Verb	Adverb
bring down	No	No	Yes	No
overturn	Yes	No	Yes	No

As verbs, bring down and overturn are synonyms defined as:

Other synonyms of bring down include overthrow, subvert.

bring down (noun)	overturn (noun)
	the act of upsetting something
	an improbable and unexpected victory

bring down (verb)	overturn (verb)
cut down on; make a reduction in	change radically
impose something unpleasant	rule against
cause to be enthusiastic	cancel officially
cause to come to the ground	turn from an upright or normal position
move something or somebody to a lower position	cause to overturn from an upright or normal position
cause the downfall of; of rulers	cause the downfall of; of rulers