- a green or bluish patina formed on copper, brass, or bronze surfaces exposed to the atmosphere for long periods of time, consisting principally of basic copper sulfate.
- a green or bluish patina formed on copper, brass, or bronze and consisting of a basic salt of copper containing both copper oxide and a copper salt
- a green or blue crystalline substance obtained by the action of acetic acid on copper and used as a fungicide and pigment; basic copper acetate
c.1300, from Old French verte grez (13c.), verte de Grece (late 12c.), literally “green of Greece,” from obsolete French verd, from Latin viridis (see verdure). The reason for it being called that is not known. In chemistry, confined to a basic copper acetate; popularly applied to the green encrustation on copper or brass exposed to the air.