fold up vs riffle

fold up is not a noun while riffle is a noun.

Word	Noun	Adjective	Verb	Adverb
fold up	No	No	Yes	No
riffle	Yes	No	Yes	No

fold up (noun)	riffle (noun)
	shuffling by splitting the pack and interweaving the two halves at their corners
	a small wave on the surface of a liquid

fold up (verb)	riffle (verb)
become folded or folded up	shuffle (playing cards) by separating the deck into two parts and riffling with the thumbs so the cards intermix
bend or lay so that one part covers the other	twitch or flutter
	stir up (water) so as to form ripples
	look through a book or other written material