slow up vs weaken

slow up and weaken both are verbs.

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

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

slow up (verb)	weaken (verb)
lose velocity; move more slowly	become weaker
cause to proceed more slowly	lessen the strength of
become slow or slower	reduce the level or intensity or size or scope of
	lessen in force or effect
	destroy property or hinder normal operations