Source : Webster's Revised Unabridged Dictionary (1913)

Impishly \Imp"ish*ly\, a.
   Having the qualities, or showing the characteristics, of an
   imp.

Impishly \Imp"ish*ly\, adv.
   In the manner of an imp.

Source : WordNet®

impishly
     adv : in an appealing but bold manner; "she asked him impishly to
           come in" [syn: {puckishly}]