an intricate knot tied by Gordius, the king of Phrygia, and cut by the sword of Alexander the Great after he heard that whoever undid it would become ruler of Asia
any very difficult problem; insoluble in its own terms
an architectural partition with a height and length greater than its thickness; used to divide or enclose an area or to support another structure; "the south wall had a small window"; "the walls were covered with pictures"
a masonry fence (as around an estate or garden); "the wall followed the road"; "he ducked behind the garden wall and waited"
a layer of material that encloses space; "the walls of the cylinder were perforated"; "the container's walls were blue"
(anatomy) a layer (a lining or membrane) that encloses a structure; "stomach walls"
anything that suggests a wall in structure or function or effect; "a wall of water"; "a wall of smoke"; "a wall of prejudice"; "negotiations ran into a brick wall"
a vertical (or almost vertical) smooth rock face (as of a cave or mountain)
a difficult or awkward situation; "his back was to the wall"; "competition was pushing them to the wall"
marriage of two people from different races or different religions or different cultures; "the families of both partners in a mixed marriage often disapprove"
an impenetrable barrier to communication or information especially as imposed by rigid censorship and secrecy; used by Winston Churchill in 1946 to describe the demarcation between democratic and communist countries
an embankment built around a space for defensive purposes; "they stormed the ramparts of the city"; "they blew the trumpet and the walls came tumbling down"