The adj sly has 1 sense (first 1 from tagged texts)
1. (1) crafty, cunning, dodgy, foxy, guileful, knavish, slick, sly, tricksy, tricky, wily -- (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 Dick"; "a wily old attorney")