shrivel up vs decrease

shrivel up is not a noun while decrease is a noun.

Word	Noun	Adjective	Verb	Adverb
shrivel up	No	No	Yes	No
decrease	Yes	No	Yes	No

As verbs, decrease is a hypernym of shrivel up; that is, decrease is a word with a broader meaning than shrivel up:

Other hypernyms of shrivel up include diminish, fall, lessen.

shrivel up (noun)	decrease (noun)
	the act of decreasing or reducing something
	the amount by which something decreases
	a change downward
	a process of becoming smaller or shorter

shrivel up (verb)	decrease (verb)
wither, as with a loss of moisture	decrease in size, extent, or range
	make become smaller