Said when someone sucks and is going no where in life. Used when someone does some dumb ass thing. Typically stated with obscene hand gestures in an ax or hockey sieve, elephant truck way.
"Dude what a wall"
After your bro drops a cup of hot chocolate. "Mark, dude, stop walling."
Looking back at your friend as you walk up a ramp. "What a wall." (supported by sieve hand jester)