backup man vs stand-in

backup man and stand-in both are nouns.

Word	Noun	Adjective	Verb	Adverb
backup man	Yes	No	No	No
stand-in	Yes	No	No	No

As nouns, backup man and stand-in are synonyms defined as:

backup man and stand-in: someone who takes the place of another (as when things get dangerous or difficult)

Other synonyms of backup man include backup, fill-in, relief, reliever, substitute.

backup man (noun)	stand-in (noun)
someone who takes the place of another (as when things get dangerous or difficult)	someone who takes the place of another (as when things get dangerous or difficult)