Source : Webster's Revised Unabridged Dictionary (1913)

Wily \Wil"y\, a. [Compar. {Wilier}; superl. {Wiliest}.] [From
   {Wile}.]
   Full of wiles, tricks, or stratagems; using craft or
   stratagem to accomplish a purpose; mischievously artful;
   subtle. ``Wily and wise.'' --Chaucer. ``The wily snake.''
   --Milton.

         This false, wily, doubling disposition of mind.
                                                  --South.

   Syn: Cunning; artful; sly; crafty. See {Cunning}.

Source : WordNet®

wily
     adj : marked by skill in deception; "cunning men often pass for
           wise"; "deep political machinations"; "a foxy scheme";
           "a slick evasive answer"; "sly as a fox"; "tricky Dik";
           "a wily old attorney" [syn: {crafty}, {cunning}, {dodgy},
            {foxy}, {guileful}, {knavish}, {slick}, {sly}, {tricksy},
            {tricky}]
     [also: {wiliest}, {wilier}]

wilier
     See {wily}