accumulate vs lump

accumulate is not a noun while lump is a noun.

Word	Noun	Adjective	Verb	Adverb
accumulate	No	No	Yes	No
lump	Yes	No	Yes	No

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

Other hyponyms of accumulate include run up, corral, collect, pull in, come up, scrape, scrape up, scratch, chunk, bale, catch, fund, fund.

accumulate (noun)	lump (noun)
	a compact mass
	a large piece of something without definite shape
	an awkward stupid person
	an abnormal protuberance or localized enlargement

accumulate (verb)	lump (verb)
increase in amount by collecting or gathering	group or chunk together in a certain order or place side by side
get or gather together	put together indiscriminately