Real Dictionary

wall
countable noun: A wall is one of the vertical sides of a building or room.

wall in American English
an upright structure of wood, stone, brick, etc., serving to enclose, divide, support, or protect
noun: any of various permanent upright constructions having a length much greater than the thickness and presenting a continuous surface except where pierced by doors, windows, etc.: used for shelter, protection, or privacy, or to subdivide interior space, to s

wall in British English
noun: a vertical construction made of stone, brick, wood, etc, with a length and height much greater than its thickness, used to enclose, divide, or support