biting; caustic; sarcastic; keen; severe.-serving to fix colors.-any corroding substance used in etching.-any substance, as alum or copperas, which, having a twofold attraction for organic fibers and coloring matter, serves as a bond of union, and thus gives fixity to, or bites in, the dyes.-any sticky matter by which the gold leaf is made to adhere.-to subject to the action of, or imbue with, a mordant; as, to mordant goods for dyeing.