excretion vs barf

excretion and barf both are nouns.

Word	Noun	Adjective	Verb	Adverb
excretion	Yes	No	No	No
barf	Yes	No	Yes	No

As nouns, barf is a hyponym of excretion; that is, barf is a word with a more specific, narrower meaning than excretion:

excretion: waste matter (as urine or sweat but especially feces) discharged from the body
barf: the matter ejected in vomiting

excretion (noun)	barf (noun)
the bodily process of discharging waste matter	the matter ejected in vomiting
waste matter (as urine or sweat but especially feces) discharged from the body

excretion (verb)	barf (verb)
	eject the contents of the stomach through the mouth