CONCRETE

(HARD MATERIAL) [noun] [U] - a very hard building material made by mixing together cement, sand, small stones and waterreinforced concretea concrete floor/path/tower blockIt's a depressing grey concrete building with tiny windows.If something is set/cast in concrete, it is fixed and cannot be changed.A concrete jungle is an ugly grey area of a city where people live in closely crowded apartment buildings and there is little space and no trees or grass.A concrete mixer is a cement mixer.See at cement (BUILDING MATERIAL).