BM vs excreta

BM and excreta both are nouns.

Word	Noun	Adjective	Verb	Adverb
BM	Yes	No	No	No
excreta	Yes	No	No	No

As nouns, excreta is a hypernym of BM; that is, excreta is a word with a broader meaning than BM:

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

Other hypernyms of BM include body waste, excrement, excretion, excretory product.

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