Mordant

Biting; caustic; sarcastic; keen; severe.

Serving to fix colors.(Dyeing & Calico Printing)

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.(Dyeing & Calico Printing)

Any sticky matter by which the gold leaf is made to adhere.(Gilding)

To subject to the action of, or imbue with, a mordant; as, to mordant goods for dyeing.