foul-up vs muff

foul-up and muff both are nouns.

Word	Noun	Adjective	Verb	Adverb
foul-up	Yes	No	No	No
muff	Yes	No	Yes	No

As nouns, muff is a hyponym of foul-up; that is, muff is a word with a more specific, narrower meaning than foul-up:

foul-up (noun)	muff (noun)
an embarrassing mistake	(sports) dropping the ball
	a warm tubular covering for the hands

foul-up (verb)	muff (verb)
	make a mess of, destroy or ruin
	fail to catch, as of a ball