noun
Usage: often capitalized M&V
: any of several basic dyes that are methyl derivatives of pararosaniline: as
a. or methyl violet B : a dye consisting essentially of pentamethyl-pararosaniline chloride and used chiefly in making organic pigments (as for printing inks) and as a biological stain — called also gentian violet ; see dye table I (under Basic Violet 1, Pigment Violet 3, and Solvent Violet 8 )
b. : crystal violet