screw up vs fluff

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

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

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

screw up (noun)	fluff (noun)
	a blunder (especially an actor's forgetting the lines)
	something of little value or significance
	any light downy material

screw up (verb)	fluff (verb)
twist into a strained configuration	ruffle (one's hair) by combing the ends towards the scalp, for a full effect
make more intense	erect or fluff up
screw or turn higher	make a mess of, destroy or ruin
make a mess of, destroy or ruin