stage business vs byplay

stage business and byplay both are nouns.

Word	Noun	Adjective	Verb	Adverb
stage business	Yes	No	No	No
byplay	Yes	No	No	No

As nouns, stage business and byplay are synonyms defined as:

stage business and byplay: incidental activity performed by an actor for dramatic effect

Other synonyms of stage business include business.

stage business (noun)	byplay (noun)
incidental activity performed by an actor for dramatic effect	incidental activity performed by an actor for dramatic effect