Vertical structure, usually solid, that defines and sometimes protects an area
A wall is a structure and a surface that defines an area; carries a load; provides security, shelter, or soundproofing; or serves a decorative purpose. There are various types of walls, including border barriers between countries, brick walls, defensive walls in fortifications, and retaining walls that hold back dirt, stone, water, or noise. Walls can also be found in buildings, where they support roofs, floors, and ceilings, enclose spaces, and provide shelter and security. The construction of walls can be categorized into framed walls and mass-walls.
https://en.wikipedia.org/wiki/Wall