Source : Webster's Revised Unabridged Dictionary (1913)

Ultraviolet \Ul`tra*vi"o*let\, a. [Pref. ultra- + violet.]
   (Physics)
   Lying outside the visible spectrum at its violet end; -- said
   of rays more refrangible than the extreme violet rays of the
   spectrum.

Source : WordNet®

ultraviolet
     adj : having or employing wavelengths shorter than light but
           longer than X-rays; lying outside the visible spectrum
           at its violet end; "ultraviolet radiation"; "an
           ultraviolet lamp"

ultraviolet
     n : radiation lying in the ultraviolet range; wave lengths
         shorter than light but longer than X rays [syn: {ultraviolet
         radiation}, {ultraviolet light}, {ultraviolet
         illumination}, {UV}]