The wall that your bed is pushed up against. The booger wall is not the entire wall, but just the section of wall that begins even with your head and runs along the edge of your matress to about mid-thigh, or as far as you can reach toward the foot end of your bed. This length of wall extends from the top edge of your mattress down the wall approx 4 inches. Boogers are picked while lying in bed and wiped in this area.
My mom was cleaning my brother's bedroom and pushed the bed away from the wall to vacuum. She was disgusted to discover his booger wall.
That little booger that you pick and roll, just before you eat or flick it. Pretty sickening in its own way cause a bastard like that shouldn't have picked his nose in the first place.
Nerd 1: Shiz, this boogerball just can't fly off my finger
Nerd 2: Just eat it and relish the saltiness