screw up vs fumble

screw up is not a noun while fumble is a noun.

Word	Noun	Adjective	Verb	Adverb
screw up	No	No	Yes	No
fumble	Yes	No	Yes	No

As verbs, screw up and fumble are synonyms defined as:

screw up (noun)	fumble (noun)
	(sports) dropping the ball

screw up (verb)	fumble (verb)
twist into a strained configuration	drop or juggle or fail to play cleanly a grounder
make more intense	feel about uncertainly or blindly
screw or turn higher	handle clumsily
make a mess of, destroy or ruin	make one's way clumsily or blindly
	make a mess of, destroy or ruin