Webster's Revised Unabridged Dictionary · 1913

Mordant

Mordant , adjective

[French, present participle of mordere to bite; Latin mordere. See Morsel.]

1.
Biting; caustic; sarcastic; keen; severe.
2.
(Dyeing & Calico Printing) Serving to fix colors.

Mordant , noun

[French, originally, biting.]

1.
Any corroding substance used in etching.
2.
(Dyeing & Calico Printing) 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.
3.
(Gilding) Any sticky matter by which the gold leaf is made to adhere.

Mordant , transitive verb

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