snap up vs grab

snap up is not a noun while grab is a noun.

Word	Noun	Adjective	Verb	Adverb
snap up	No	No	Yes	No
grab	Yes	No	Yes	No

As verbs, snap up and grab are synonyms defined as:

Other synonyms of snap up include snaffle.

snap up (noun)	grab (noun)
	the act of catching an object with the hands
	a mechanical device for gripping an object

snap up (verb)	grab (verb)
get hold of or seize quickly and easily	capture the attention or imagination of
	take hold of so as to seize or restrain or stop the motion of
	take or grasp suddenly
	make a grasping or snatching motion with the hand
	get hold of or seize quickly and easily
	obtain illegally or unscrupulously