rack up vs fill

rack up is not a noun while fill is a noun.

Word	Noun	Adjective	Verb	Adverb
rack up	No	No	Yes	No
fill	Yes	No	Yes	No

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

Other hypernyms of rack up include fill up.

rack up (noun)	fill (noun)
	a quantity sufficient to satisfy
	any material that fills a space or container

rack up (verb)	fill (verb)
supply a rack with feed for (horses or other animals)	become full
defeat thoroughly	make full, also in a metaphorical sense
gain points in a game	plug with a substance
place in a rack	fill to satisfaction
	eat until one is sated
	fill, satisfy or meet a want or need or condition or restriction
	assume, as of positions or roles
	appoint someone to (a position or a job)
	occupy the whole of