slow up vs delay

slow up is not a noun while delay is a noun.

Word	Noun	Adjective	Verb	Adverb
slow up	No	No	Yes	No
delay	Yes	No	Yes	No

As verbs, delay is a hyponym of slow up; that is, delay is a word with a more specific, narrower meaning than slow up:

Other hyponyms of slow up include slow, slow down, slow up, detain, hold up.

slow up (noun)	delay (noun)
	the act of delaying; inactivity resulting in something being put off until a later time
	time during which some action is awaited

slow up (verb)	delay (verb)
lose velocity; move more slowly	cause to be slowed down or delayed
cause to proceed more slowly	stop or halt
become slow or slower	slow the growth or development of
	act later than planned, scheduled, or required