hold up vs prop

hold up is not a noun while prop is a noun.

Word	Noun	Adjective	Verb	Adverb
hold up	No	No	Yes	No
prop	Yes	No	Yes	No

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

Other hyponyms of hold up include scaffold, block, carry, chock, buoy, buoy up, pole, bracket, underpin, prop up, shore, shore up, truss, brace.

hold up (noun)	prop (noun)
	a support placed beneath or against something to keep it from shaking or falling
	a propeller that rotates to push against air
	any movable articles or objects used on the set of a play or movie

hold up (verb)	prop (verb)
cause to be slowed down or delayed	support by placing against something solid or rigid
be the physical support of; carry the weight of
hold up something as an example; hold up one's achievements for admiration
rob at gunpoint or by means of some other threat
continue to live and avoid dying
resist or withstand wear, criticism, etc.
resist or confront with resistance