fluff vs flub

fluff and flub both are nouns.

Word	Noun	Adjective	Verb	Adverb
fluff	Yes	No	Yes	No
flub	Yes	No	Yes	No

As nouns, flub is a hypernym of fluff; that is, flub is a word with a broader meaning than fluff:

Other hypernyms of fluff include bloomer, blooper, blunder, boner, boo-boo, botch, bungle, foul-up, fuckup, pratfall.

As verbs, fluff and flub are synonyms defined as:

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

fluff (verb)	flub (verb)
ruffle (one's hair) by combing the ends towards the scalp, for a full effect	make a mess of, destroy or ruin
erect or fluff up
make a mess of, destroy or ruin