undergo vs labor

undergo is not a noun while labor is a noun.

Word	Noun	Adjective	Verb	Adverb
undergo	No	No	Yes	No
labor	Yes	No	Yes	No

As verbs, labor is a hyponym of undergo; that is, labor is a word with a more specific, narrower meaning than undergo:

Other hyponyms of undergo include respire, labour, submit, take, experience, get, have, receive, experience, go through, see.

undergo (noun)	labor (noun)
	productive work (especially physical work done for wages)
	any piece of work that is undertaken or attempted
	a social class comprising those who do manual labor or work for wages
	an organized attempt by workers to improve their status by united action (particularly via labor unions) or the leaders of this movement
	concluding state of pregnancy; from the onset of contractions to the birth of a child

undergo (verb)	labor (verb)
go through	undergo the efforts of childbirth
	work hard
	strive and make an effort to reach a goal