Source : Webster's Revised Unabridged Dictionary (1913)

Elfish \Elf"ish\, a.
   Of or relating to the elves; elflike; implike; weird;
   scarcely human; mischievous, as though caused by elves.
   ``Elfish light.'' --Coleridge.

         The elfish intelligence that was so familiar an
         expression on her small physiognomy.     --Hawthorne.

Source : WordNet®

elfish
     adj : usually good-naturedly mischievous; "perpetrated a practical
           joke with elfin delight"; "elvish tricks" [syn: {elfin},
            {elvish}]