over a wall; across a fence
Describes an action or state that takes place over or across a wall or fence, often implying communication, passing objects, or looking over.
I talked with the neighbor over the fence.
塀越しにボールを投げ入れた。
I threw the ball over the wall.
Compound of 塀 (へい, 'wall, fence') and 越し (ごし, 'across, over').