noun
: any sulfate of copper ; specifically : the normal sulfate CuSO 4 , white when anhydrous but best known as the blue crystalline pentahydrate CuSO 4 .5H 2 O, that is made by roasting copper sulfide ores and by the action of sulfuric acid on copper or copper oxide and that is used chiefly as a fungicide and algicide, in dyeing and printing, in making pigments and other compounds, and in electric batteries — see bordeaux mixture