A1[C]a vertical structure, often made of stone or brick, that divides or surrounds something: The walls in this apartment are so thin you can hear just about every word the neighbours say.The walls look a bit bare - can't we put some pictures up?We had to climb over a ten-foot wall to get into the garden.The Berlin Wall came down in 1989.Walls and parts of walls›[C]any outer part of a hollow structure in the body: the wall of the womb/stomachan artery wallSubstances and structures in the body›[C]a mass of people or things formed in such a way that you cannot get through or past them: The demonstrators formed a solid wall to stop the police from getting past them.Groups of people›[S]literarya large, powerful, usually fast moving mass of something: After the rains, the houses were washed away by a wall of mud/water.Masses and large amounts of things›[S]a way of feeling or behaving that completely prevents two groups of people from communicating with or understanding each other: There is a wall of mistrust between the two groups.Difficult things and peoplePreventing and impeding