n. 1. a. Any of various low-growing herbs of the genus Viola, having short-spurred, irregular flowers that are characteristically purplish-blue but sometimes yellow or white.
b. Any of several similar plants, such as an African violet.
2. The hue at the short-wavelength end of the visible spectrum, evoked in the human observer by radiant energy with wavelengths of approximately 380 to 420 nanometers; any of a group of colors, reddish-blue in hue, that may vary in lightness and saturation.