Definition from Wiktionary, the free dictionary
biting or caustic
mordant (plural mordants)
- Any substance used to facilitate the fixing of a dye to a fibre; usually a metallic compound which reacts with the dye using chelation.
- 1964, In dyeing two mediums are required, the colouring matter and the mordant which fixes the dye in the wool. — L.F. Salzman, English Industries of the Middle Ages, p. 208.
- Any corrosive substance used in etching.
a substance used to facilitate dye fixing
See also 
- Present participle of mordre.