mor·dant 
(môrdnt)
(môrdnt)adj.
1.
a. Bitingly sarcastic: mordant satire.
b. Incisive and trenchant: an inquisitor's mordant questioning.
2. Bitingly painful.
3. Serving to fix colors in dyeing.
n.
1. A reagent, such as tannic acid, that fixes dyes to cells, tissues, or textiles or other materials.
2. A corrosive substance, such as an acid, used in etching.
tr.v. mor·dant·ed, mor·dant·ing, mor·dants
To treat with a mordant.
[French, from Old French, present participle of mordre, to bite, from Vulgar Latin *mordere, from Latin mordēre; see mer- in the Appendix of Indo-European roots.]
mordan·cy n.
mordant·ly adv.