scrub up vs scrub

scrub up is not a noun while scrub is a noun.

Word	Noun	Adjective	Verb	Adverb
scrub up	No	No	Yes	No
scrub	Yes	Yes	Yes	No

As verbs, scrub up and scrub are synonyms defined as:

scrub up (noun)	scrub (noun)
	the act of cleaning a surface by rubbing it with a brush and soap and water
	dense vegetation consisting of stunted trees or bushes

scrub up (adjective)	scrub (adjective)
	(of domestic animals) not selectively bred

scrub up (verb)	scrub (verb)
wash thoroughly	wash thoroughly
	clean with hard rubbing
	postpone indefinitely or annul something that was scheduled