stomach flu vs intestinal flu

stomach flu and intestinal flu both are nouns.

Word	Noun	Adjective	Verb	Adverb
stomach flu	Yes	No	No	No
intestinal flu	Yes	No	No	No

As nouns, stomach flu and intestinal flu are synonyms defined as:

stomach flu and intestinal flu: inflammation of the stomach and intestines; can be caused by Salmonella enteritidis

Other synonyms of stomach flu include gastroenteritis.

stomach flu (noun)	intestinal flu (noun)
inflammation of the stomach and intestines; can be caused by Salmonella enteritidis	inflammation of the stomach and intestines; can be caused by Salmonella enteritidis