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1.
secretive friend
Wallup: i'm afraid you may know something you were not supposed to.
Friend: wut?
Wallup: just know you will always be my bestie because you know too much. Otherwise, I'm afraid I have to kill you.
by friendsForever June 19, 2013
 
2.
v:

"Wall up" is the term used when engaging in lingo de graffiti. when used it is referring to creating new graffiti or tagging up a wall. Starting or beginning a new piece of street art.
Wall up:

Hey friends, i seen a neat wall with a lot of empty space; Wallup!
by Graffiti 2LOb February 14, 2013
 
3.
When you do push ups against the wall in the shower.
"I never have time to exercise anymore!" "I know, that's why I always do wallups in the morning in the shower...."
by tadpole0763 April 17, 2010
 
4.
the vagina
"You all have an interesting wallup!"

"Goddamn that wallup's wide!"
by Mark October 19, 2003