gentian violet noun 2adjective 1forms 3 noun2 •Also known as crystal violet, a chemical dye used in the Gram stain test, and is also a fungicide. Chemically: hexamethyl pararosaniline chloride, C₂₅H₃₀ClN₃ •A violet colour similar to the gentian flower. adjective1 •Having a violet colour similar to the gentian flower. formsgentian violets · more gentian violet · most gentian violet