From WordNet (r) 2.0 (August 2003) [wn]:
knavish
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, slick, sly, tricksy,
tricky, wily]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Knavish \Knav"ish\, a.
1. Like or characteristic of a knave[3]; given to knavery;
trickish; fraudulent; dishonest; villainous; as, a knavish
fellow, or a knavish trick. "Knavish politicians."
--Macaulay.
[1913 Webster]
2. Mischievous; roguish; waggish; rascally.
[1913 Webster]
Cupid is knavish lad,
Thus to make poor females mad. --Shak.
[1913 Webster]