fluff vs loosen

fluff is a noun but loosen is not a noun.

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

As verbs, loosen is a hypernym of fluff; that is, loosen is a word with a broader meaning than fluff:

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

fluff (verb)	loosen (verb)
ruffle (one's hair) by combing the ends towards the scalp, for a full effect	become loose or looser or less tight
erect or fluff up	make loose or looser
make a mess of, destroy or ruin	make less dense
	disentangle and raise the fibers of
	cause to become loose
	become less severe or strict
	make less severe or strict