- 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 support floors, roofs, or the like, to retain earth, to fence in an area, etc.
- Usually walls. a rampart raised for defensive purposes.
- an immaterial or intangible barrier, obstruction, etc., suggesting a wall: a wall of prejudice.
- a wall-like, enclosing part, thing, mass, etc.: a wall of fire; a wall of troops.
- an embankment to prevent flooding, as a levee or sea wall.
- the outermost film or layer of structural material protecting, surrounding, and defining the physical limits of an object: the wall of a blood cell.
- Soccer. a line of defenders standing shoulder to shoulder in an attempt to block a free kick with their bodies.