Source : Webster's Revised Unabridged Dictionary (1913)

Exceptional \Ex*cep"tion*al\, a. [Cf. F. exceptionnel.]
   Forming an exception; not ordinary; uncommon; rare; hence,
   better than the average; superior. --Lyell.

         This particular spot had exceptional advantages.
                                                  --Jowett (Th.
                                                  )
   -- {Ex*cep"tion*al*ly}, adv.

Source : WordNet®

exceptionally
     adv : to an exceptional degree; "it worked exceptionally well"