scrunch vs ruck up

scrunch is a noun but ruck up is not a noun.

Word	Noun	Adjective	Verb	Adverb
scrunch	Yes	No	Yes	No
ruck up	No	No	Yes	No

As verbs, ruck up is a hyponym of scrunch; that is, ruck up is a word with a more specific, narrower meaning than scrunch:

scrunch: make wrinkles or creases on a smooth surface; make a pressed, folded or wrinkled line in; `crisp' is archaic
ruck up: become wrinkled or drawn together

Other hyponyms of scrunch include cockle, crumple, knit, pucker, rumple, pucker, ruck.

scrunch (noun)	ruck up (noun)
a crunching noise

scrunch (verb)	ruck up (verb)
make wrinkles or creases on a smooth surface; make a pressed, folded or wrinkled line in; `crisp' is archaic	become wrinkled or drawn together
sit on one's heels
make a noise typical of an engine lacking lubricants