fecal matter vs muck

fecal matter and muck both are nouns.

Word	Noun	Adjective	Verb	Adverb
fecal matter	Yes	No	No	No
muck	Yes	No	Yes	No

As nouns, muck is a hyponym of fecal matter; that is, muck is a word with a more specific, narrower meaning than fecal matter:

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

fecal matter (noun)	muck (noun)
solid excretory product evacuated from the bowels	any thick, viscous matter
	fecal matter of animals

fecal matter (verb)	muck (verb)
	remove muck, clear away muck, as in a mine
	soil with mud, muck, or mire
	spread manure, as for fertilization