Source : Webster's Revised Unabridged Dictionary (1913)

Stunning \Stun"ning\, a.
   1. Overpowering consciousness; overpowering the senses;
      especially, overpowering the sense of hearing; confounding
      with noise.

   2. Striking or overpowering with astonishment, especially on
      account of excellence; as, stunning poetry. [Slang] --C.
      Kingsley. -- {Stun"ning*ly}, adv. [Slang]

Source : WordNet®

stunningly
     adv : in a spectacular manner; "the area was spectacularly scenic"
           [syn: {spectacularly}]