What does "mural" mean?

Mural: Resembling a wall; perpendicular or steep; as, a mural precipice. Mural circle (Astron.), a graduated circle, in the plane of the meridian, attached permanently to a perpendicular wall; -- used for measuring arcs of the meridian. See Circle, n., 3. -- Mural crown (Rom. Antiq.), a golden crown, or circle of gold indented so as to resemble a battlement, bestowed on him who first mounted the wall of a besieged place, and there lodged a standard.