slow down vs hold up

slow down and hold up both are verbs.

Word	Noun	Adjective	Verb	Adverb
slow down	No	No	Yes	No
hold up	No	No	Yes	No

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

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

slow down (verb)	hold up (verb)
become less tense, rest, or take one's ease	cause to be slowed down or delayed
lose velocity; move more slowly	be the physical support of; carry the weight of
become slow or slower	hold up something as an example; hold up one's achievements for admiration
reduce the speed of	rob at gunpoint or by means of some other threat
cause to proceed more slowly	continue to live and avoid dying
	resist or withstand wear, criticism, etc.
	resist or confront with resistance