riffle vs fold up

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

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

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

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