exercising vs workout

exercising and workout both are nouns.

Word	Noun	Adjective	Verb	Adverb
exercising	Yes	No	No	No
workout	Yes	No	No	No

As nouns, exercising and workout are synonyms defined as:

exercising and workout: the activity of exerting your muscles in various ways to keep fit

Other synonyms of exercising include exercise, physical exercise, physical exertion.

exercising (noun)	workout (noun)
the activity of exerting your muscles in various ways to keep fit	the activity of exerting your muscles in various ways to keep fit