Definition of Plaster

• a mixture of lime or gypsum with sand and water; hardens into a smooth solid; used to cover walls and ceilings
• any of several gypsum cements; a white powder (a form of calcium sulphate) that forms a paste when mixed with water and hardens into a solid; used in making molds and sculptures and casts for broken limbs
• a surface of hardened plaster (as on a wall or ceiling); "there were cracks in the plaster"