BM vs dog shit

BM and dog shit both are nouns.

Word	Noun	Adjective	Verb	Adverb
BM	Yes	No	No	No
dog shit	Yes	No	No	No

As nouns, dog shit is a hyponym of BM; that is, dog shit is a word with a more specific, narrower meaning than BM:

Other hyponyms of BM include dog do, dog turd, doggy do, crap, dirt, poop, shit, shite, turd, droppings, dung, muck, meconium, melaena, melena.

BM (noun)	dog shit (noun)
solid excretory product evacuated from the bowels	fecal droppings from a dog