pile up vs pile

pile up is not a noun while pile is a noun.

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

pile up (noun)	pile (noun)
	a nuclear reactor that uses controlled nuclear fission to generate energy
	battery consisting of voltaic cells arranged in series; the earliest electric battery devised by Volta
	the yarn (as in a rug or velvet or corduroy) that stands up from the weave
	a column of wood or steel or concrete that is driven into the ground to provide support for a structure
	fine soft dense hair (as the fine short hair of cattle or deer or the wool of sheep or the undercoat of certain dogs)
	a collection of objects laid on top of each other
	a large sum of money (especially as pay or profit)
	(often followed by `of') a large number or amount or extent

pile up (verb)	pile (verb)
increase in amount by collecting or gathering	arrange in stacks
arrange into piles or stacks	place or lay as if in a pile
get or gather together	press tightly together or cram