defeat vs overcome

defeat is a noun but overcome is not a noun.

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

As verbs, defeat and overcome are synonyms defined as:

Other synonyms of defeat include get the better of.

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

defeat (verb)	overcome (verb)
win a victory over	get on top of; deal with successfully
thwart the passage of	overcome, usually through no fault or weakness of the person that is overcome
	win a victory over
	overcome, as with emotions or perceptual stimuli