stand firm vs hold up

stand firm and hold up both are verbs.

Word	Noun	Adjective	Verb	Adverb
stand firm	No	No	Yes	No
hold up	No	No	Yes	No

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

Other hyponyms of stand firm include stand out, stand up, outbrave, hold off, remain firm, stand, defy, hold, withstand.

stand firm (verb)	hold up (verb)
refuse to abandon one's opinion or belief	cause to be slowed down or delayed
stand up or offer resistance to somebody or something	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