excretion vs waste matter

excretion and waste matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
excretion	Yes	No	No	No
waste matter	Yes	No	No	No

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

excretion: waste matter (as urine or sweat but especially feces) discharged from the body
waste matter: any materials unused and rejected as worthless or unwanted

Other hypernyms of excretion include waste, waste material, waste product.

excretion (noun)	waste matter (noun)
the bodily process of discharging waste matter	any materials unused and rejected as worthless or unwanted
waste matter (as urine or sweat but especially feces) discharged from the body