intestinal flu vs gastroenteritis

intestinal flu and gastroenteritis both are nouns.

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

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

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

Other synonyms of intestinal flu include stomach flu.

intestinal flu (noun)	gastroenteritis (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