excretion vs piss

excretion and piss both are nouns.

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

As nouns, piss is a hyponym of excretion; that is, piss 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
piss: liquid excretory product

excretion (noun)	piss (noun)
the bodily process of discharging waste matter	informal terms for urination
waste matter (as urine or sweat but especially feces) discharged from the body	liquid excretory product

excretion (verb)	piss (verb)
	eliminate urine