hold up vs truss

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

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

As verbs, truss is a hyponym of hold up; that is, truss 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, prop up, shore, shore up, brace.

hold up (noun)	truss (noun)
	a framework of beams (rafters, posts, struts) forming a rigid structure that supports a roof or bridge or other structure
	(medicine) a bandage consisting of a pad and belt; worn to hold a hernia in place by pressure
	(architecture) a triangular bracket of brick or stone (usually of slight extent)

hold up (verb)	truss (verb)
cause to be slowed down or delayed	support structurally
be the physical support of; carry the weight of	tie the wings and legs of a bird before cooking it
hold up something as an example; hold up one's achievements for admiration	secure with or as if with ropes
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