grime vs muck up

grime is a noun but muck up is not a noun.

Word	Noun	Adjective	Verb	Adverb
grime	Yes	No	Yes	No
muck up	No	No	Yes	No

As verbs, muck up is a hyponym of grime; that is, muck up is a word with a more specific, narrower meaning than grime:

Other hyponyms of grime include foul, contaminate, foul, pollute, smear, slime, muddy, muddy up, splash, mire, muck, mud, crock, blemish, spot.

grime (noun)	muck up (noun)
anything regarded as making something unclean

grime (verb)	muck up (verb)
make soiled, filthy, or dirty	soil with mud, muck, or mire
	make a mess of, destroy or ruin