fecal matter vs body waste

fecal matter and body waste both are nouns.

Word	Noun	Adjective	Verb	Adverb
fecal matter	Yes	No	No	No
body waste	Yes	No	No	No

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

fecal matter: solid excretory product evacuated from the bowels
body waste: waste matter (as urine or sweat but especially feces) discharged from the body

Other hypernyms of fecal matter include excrement, excreta, excretion, excretory product.

fecal matter (noun)	body waste (noun)
solid excretory product evacuated from the bowels	waste matter (as urine or sweat but especially feces) discharged from the body