piss vs excretion

piss and excretion both are nouns.

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

As nouns, excretion is a hypernym of piss; that is, excretion is a word with a broader meaning than piss:

piss: liquid excretory product
excretion: waste matter (as urine or sweat but especially feces) discharged from the body

Other hypernyms of piss include body waste, excrement, excreta, excretory product.

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

piss (verb)	excretion (verb)
eliminate urine