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rock milk

American

noun

a white, powdery surface crust of calcite, formed by efflorescence in limestone caves and fissures.

Etymology

Origin of rock milk

First recorded in 1795–1805

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.