excrement vs waste matter

excrement and waste matter both are nouns.

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

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

excrement: 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 excrement include waste, waste material, waste product.

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