Gŷp'sum, n.

n. [Lat. gypsum, Gr. γύψος, Ar. djibsîn, Per. djabsîn, Chald. giphēs.] (Min.) A mineral consisting of sulphate of lime, and 21 per cent. of water. The transparent varieties are called selenite, and the fine, massive varieties, alabaster. Gypsum, when calcined, forms plaster of Paris; it is otherwise improperly so called.