stomach upset vs indigestion

stomach upset and indigestion both are nouns.

Word	Noun	Adjective	Verb	Adverb
stomach upset	Yes	No	No	No
indigestion	Yes	No	No	No

As nouns, stomach upset and indigestion are synonyms defined as:

stomach upset and indigestion: a disorder of digestive function characterized by discomfort or heartburn or nausea

Other synonyms of stomach upset include dyspepsia, upset stomach.

stomach upset (noun)	indigestion (noun)
a disorder of digestive function characterized by discomfort or heartburn or nausea	a disorder of digestive function characterized by discomfort or heartburn or nausea