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2.
(n.) A humorous term used to describe an action in which before departing for a destination a person will make a mental checklist of any items needed or wanted on said travel; attained from the action of patting one's back pockets in order validate the items existence.
Bob: Have you done an ass check yet?

John: *pats pockets* keys...check, wallet....check, ass....check!
by Atrium's atrium January 20, 2011
 
1.
The quick glance taken to scope the goods from behind when someone walks by.
Mike: Will, that guy just caught you doing an asscheck.
Will: He was so cute and smiled when he walked by. I just had to look at his booty.
by Kuch March 20, 2008