plaster of Paris

UK: /ˌplɑːstərəvˈpærɪs/ US: /ˈplæstər əv ˈpærɪs/

WordReference Random House Learner's Dictionary of American English © 2026

plas•ter of Par•is (or par•is)/ˈplæstər əv ˈpærɪs/  n. [uncountable]

1. Fine Art a white powdery substance, used as a base for gypsum plasters and as a material for mixing with water to make fine or decorative casts.

WordReference Random House Unabridged Dictionary of American English © 2026

plas′ter of Par′is, 

1. Fine Art 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, plas′ter of par′is. 

• 1375–1425; late Middle English; so called because prepared from the gypsum of Paris, France

Collins Concise English Dictionary © HarperCollins Publishers::

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

Etymology: 15th Century: from Medieval Latin plastrum parisiense, originally made from the gypsum of Paris