plaster of Paris

noun
1.
calcined gypsum in white, powdery form, used as a base for gypsum plasters, as an additive of lime plasters, and as a material for making fine and ornamental casts: characterized by its ability to set rapidly when mixed with water.
Also, plaster of paris.
Origin
1375-1425; late Middle English; so called because prepared from the gypsum of Paris, France
British Dictionary definitions for plaster of Paris

plaster of Paris

noun
1.
a white powder that sets to a hard solid when mixed with water, used for making sculptures and casts, as an additive for lime plasters, and for making casts for setting broken limbs. It is usually the hemihydrate of calcium sulphate, 2CaSO4.H2O
2.
the hard plaster produced when this powder is mixed with water: a fully hydrated form of calcium sulphate
Sometimes shortened to plaster
Word Origin
C15: from Medieval Latin plastrum parisiense, originally made from the gypsum of Paris
Word Origin and History for plaster of Paris
n.

mid-15c.; originally it was made from the extensive gypsum deposits of Montmartre in Paris.

plaster of Paris in Medicine

plaster of Paris plaster of Par·is (pār'ĭs)
n.
Any of a group of gypsum cements, essentially hemihydrated calcium sulfate, a white powder that forms a paste when mixed with water and hardens into a solid, used in making casts and molds.

plaster of Paris in Science
plaster of Paris
  (plās'tər)   
A form of calcium phosphate derived from gypsum. It is mixed with water to make casts and molds.