The Collaborative International Dictionary of English v.0.48:

Radiance \Ra"di*ance\ (r[=a]"d[i^]*ans), Radiancy \Ra"di*an*cy\
   (r[=a]"d[i^]*an*s[y^]), n.
   The quality of being radiant; brilliancy; effulgence; vivid
   brightness; as, the radiance of the sun.
   [1913 Webster]

         Girt with omnipotence, with radiance crowned. --Milton.
   [1913 Webster]

         What radiancy of glory,
         What light beyond compare !              --Neale.
   [1913 Webster]

   Syn: Luster; brilliancy; splendor; glare; glitter.
        [1913 Webster]

WordNet (r) 3.0 (2006):

radiance
    n 1: the amount of electromagnetic radiation leaving or arriving
         at a point on a surface [syn: radiance, glow,
         glowing]
    2: the quality of being bright and sending out rays of light
       [syn: radiance, radiancy, shine, effulgence,
       refulgence, refulgency]
    3: an attractive combination of good health and happiness; "the
       radiance of her countenance"