n. A preparation for blacking boots and shoes, usually made of powdered bone-black, spermor linseed-oil, molasses, sour beer or vinegar, oil of vitriol, and copperas.n. In leather-working, any one of a number of preparations used in dyeing or staining leather black.n. The name given by founders to a black wash, composed of clay, water, and powdered charcoal, with which cores and loam-molds are coated, to give the requisite smoothness to the surfaces which come into contact with the melted metal.