keep down vs vomit

keep down is not a noun while vomit is a noun.

Word	Noun	Adjective	Verb	Adverb
keep down	No	No	Yes	No
vomit	Yes	No	Yes	No

keep down (noun)	vomit (noun)
	the reflex act of ejecting the contents of the stomach through the mouth
	a medicine that induces nausea and vomiting
	the matter ejected in vomiting

keep down (verb)	vomit (verb)
manage not to throw up	eject the contents of the stomach through the mouth
place a limit on the number of
put down by force or intimidation