excrement vs barf

excrement and barf both are nouns.

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

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

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

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

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