verdigris

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A blue or green powder consisting of basic cupric acetate used as a paint pigment and fungicide.
2. n. A green patina or crust of copper sulfate or copper chloride formed on copper, brass, and bronze exposed to air or seawater for long periods of time.

Century Dictionary and Cyclopedia

1. n. A substance obtained by exposing plates of copper to the air in contact with acetic acid, and much used as a pigment, as a mordant in dyeing wool black, in calico-printing, and in gilding, in several processes in the chemical arts, and in medicine. Verdigris, like all the compounds into which copper enters, is poisonous; and it is very apt to form on the surface of copper utensils, owing to the action of vegetable juices. It is, chemically, a crystalline salt known as the basic acetate of copper. It ranges in hue from green to greenish-blue, according to the proportions of acetic acid and copper contained. As a pigmeut it is fairly permanent, but has little body, and is generally used only as a glazing color.
2. To cause to be coated with verdigris; cover or coat with verdigris.

Wiktionary

1. n. A blue-green patina that forms on copper-containing metals.
2. n. Copper acetate.
3. n. The colour of this patina or material.

GNU Webster's 1913

1. n. A green poisonous substance used as a pigment and drug, obtained by the action of acetic acid on copper, and consisting essentially of a complex mixture of several basic copper acetates.
2. n. The green rust formed on copper.
3. v. To cover, or coat, with verdigris.

WordNet 3.0

1. n. a blue or green powder used as a paint pigment
2. v. color verdigris
3. n. a green patina that forms on copper or brass or bronze that has been exposed to the air or water for long periods of time