muck up vs muff

muck up is not a noun while muff is a noun.

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

As verbs, muck up and muff are synonyms defined as:

muck up (noun)	muff (noun)
	(sports) dropping the ball
	a warm tubular covering for the hands

muck up (verb)	muff (verb)
soil with mud, muck, or mire	make a mess of, destroy or ruin
make a mess of, destroy or ruin	fail to catch, as of a ball