vanquish vs defeat

vanquish is not a noun while defeat is a noun.

Word	Noun	Adjective	Verb	Adverb
vanquish	No	No	Yes	No
defeat	Yes	No	Yes	No

As verbs, defeat is a hypernym of vanquish; that is, defeat is a word with a broader meaning than vanquish:

Other hypernyms of vanquish include get the better of, overcome.

vanquish (noun)	defeat (noun)
	an unsuccessful ending to a struggle or contest
	the feeling that accompanies an experience of being thwarted in attaining your goals

vanquish (verb)	defeat (verb)
come out better in a competition, race, or conflict	win a victory over
	thwart the passage of