overrule vs overturn

overrule is not a noun while overturn is a noun.

Word	Noun	Adjective	Verb	Adverb
overrule	No	No	Yes	No
overturn	Yes	No	Yes	No

As verbs, overrule and overturn are synonyms defined as:

Other synonyms of overrule include override, overthrow, reverse.

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

overrule (verb)	overturn (verb)
rule against	change radically
	rule against
	cancel officially
	turn from an upright or normal position
	cause to overturn from an upright or normal position
	cause the downfall of; of rulers