armed robbery vs holdup

armed robbery and holdup both are nouns.

Word	Noun	Adjective	Verb	Adverb
armed robbery	Yes	No	No	No
holdup	Yes	No	No	No

As nouns, armed robbery and holdup are synonyms defined as:

Other synonyms of armed robbery include heist, stickup.

armed robbery (noun)	holdup (noun)
robbery at gunpoint	robbery at gunpoint
	the act of delaying; inactivity resulting in something being put off until a later time