scrape vs pile up

scrape is a noun but pile up is not a noun.

Word	Noun	Adjective	Verb	Adverb
scrape	Yes	No	Yes	No
pile up	No	No	Yes	No

As verbs, pile up is a hypernym of scrape; that is, pile up is a word with a broader meaning than scrape:

Other hypernyms of scrape include accumulate, amass, collect, compile, hoard, roll up.

scrape (noun)	pile up (noun)
an indication of damage
a deep bow with the foot drawn backwards (indicating excessive humility)
a harsh noise made by scraping
an abraded area where the skin is torn or worn off

scrape (verb)	pile up (verb)
scratch repeatedly	increase in amount by collecting or gathering
bruise, cut, or injure the skin or the surface of	arrange into piles or stacks
cut the surface of; wear away the surface of	get or gather together
gather (money or other resources) together over time
make by scraping
bend the knees and bow in a servile manner