upset stomach vs indigestion

upset stomach and indigestion both are nouns.

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

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

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

Other synonyms of upset stomach include dyspepsia, stomach upset.

upset stomach (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