Brilliance
A timbre descriptor (treble range) in audio equipment assessment: Treble or high frequency extension.
Scale applied in listening tests: A little: As if you hear music through a door, muffled, blurred or dull. A lot: Crystal-clear reproduction extended treble range with airy and open treble. Lightness, purity and clarity with space for instruments. Clarity in the upper frequencies without being sharp or shrill and without distortion.
[Reference: Report ITU-R BS.2399-0]