Source : Webster's Revised Unabridged Dictionary (1913)

Uncommon \Un*com"mon\, a.
   Not common; unusual; infrequent; rare; hence, remarkable;
   strange; as, an uncommon season; an uncommon degree of cold
   or heat; uncommon courage.

   Syn: Rare; scarce; infrequent; unwonted. -- {Un*com"mon*ly},
        adv. -- {Un*com"mon*ness}, n.

Source : WordNet®

uncommonly
     adv : exceptionally; "a common remedy is uncommonly difficult to
           find"