ETYM Pref. ultra- + violet.
Having or employing wavelengths shorter than light but longer than X-rays; lying outside the visible spectrum at its violet end.

Radiation lying in the ultraviolet range; wave lengths shorter than light but longer than X rays; SYN. ultraviolet radiation, ultraviolet light, ultraviolet illumination, uv.
That portion of the electromagnetic spectrum below blue light (380 nanometers).