Wall

1. An upright structure of masonry, wood, plaster, or other building material serving to enclose, divide, or protect an area, especially a vertical construction forming an inner partition or exterior siding of a building. We built a wall of concrete blocks to hold the bank on the edge of our lawn.
2. Often walls. A continuous structure of masonry or other material forming a rampart and built for defensive purposes. The Chinese built walls around most of the cities in ancient days.