noun
: any oxide of copper: as
a. : the oxide Cu 2 O that occurs naturally as cuprite and is obtained as red or yellow crystals or powder by oxidation of copper in a furnace or by electrolysis and that is used chiefly as a pigment (as in ceramics and in antifouling paints) and as a seed disinfectant and fungicide — called also copper(I) oxide, cuprous oxide, red copper oxide
b. : the monoxide CuO that occurs naturally as paramelaconite and tenorite, is obtained usually in black amorphous form by oxidizing copper, and is used chiefly in preparing cuprammonium solution, as a pigment in ceramics, as a catalyst for hydrogenations, and in chemical analysis — called also black copper oxide, copper(II) oxide, cupric oxide