gypsum /jipˈsəm or gipˈsəm/ noun A soft mineral, hydrated calcium sulphate, source of plaster of Paris and other plasters ORIGIN: L, from Gr gypsos chalk gypˈseous adjective gypsifˈerous adjective Producing or containing gypsum gypsum block noun A building block (usu hollow) made of gypsum plaster gypsum plasterboard (or simply plasterboard) noun Building-board consisting of a core of gypsum or anhydrous gypsum plaster between two sheets of paper |