pile up vs increase

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

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

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

pile up (noun)	increase (noun)
	the act of increasing something
	the amount by which something increases
	a change resulting in an increase
	a process of becoming larger or longer or more numerous or more important
	a quantity that is added

pile up (verb)	increase (verb)
increase in amount by collecting or gathering	become bigger or greater in amount
arrange into piles or stacks	make bigger or more
get or gather together