bring down vs overthrow

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

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

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

Other synonyms of bring down include overturn, subvert.

bring down (noun)	overthrow (noun)
	the termination of a ruler or institution (especially by force)
	the act of disturbing the mind or body

bring down (verb)	overthrow (verb)
cut down on; make a reduction in	rule against
impose something unpleasant	cause the downfall of; of rulers
cause to be enthusiastic
cause to come to the ground
move something or somebody to a lower position
cause the downfall of; of rulers