To have sex with someone against a wall.
Sometimes this happens by accident in the heat of the moment, it can also be planned, and happens when you're wasted from time to time.
Walled is not the same as closeted
, a wall in a closet is a closet wall, therefore no walling has happened.
example1: Jeff walled Christina last night, I could hear it through the wall.
example2: I walled Christina hard last night.
example2: Jeff walled me last night, I liked it.