[sly] adj sli.er or sly.er ; sli.est or sly.est [ME sli, fr. ON sloegr; akin to OE slean to strike--more at slay] (13c) 1 chiefly dial a: wise in practical affairs b: displaying cleverness: ingenious
2. a: clever in concealing one's aims or ends: furtive "the ~ fox" b: lacking in straightforwardness and candor: dissembling "a ~ scheme"
3: lightly mischievous: roguish "a ~ jest" "a ~ smile" -- sly.ly adv -- sly.ness n -- on the sly : in a manner intended to avoid notice syn sly, cunning, crafty, wily, tricky, foxy, artful, slick mean attaining or seeking to attain one's ends by guileful or devious means. sly implies furtiveness, lack of candor, and skill in concealing one's aims and methods "a sly corporate raider". cunning suggests the inventive use of sometimes limited intelligence in overreaching or circumventing "the cunning fox avoided the trap". crafty implies cleverness and subtlety of method "a crafty lefthander". wily implies skill and deception in maneuvering "the wily fugitive escaped the posse". tricky is more likely to suggest shiftiness and unreliability than skill in deception and maneuvering "a tricky political operative". foxy implies a shrewd and wary craftiness usu. involving devious dealing "a foxy publicity man planting stories". artful implies indirectness in dealing and often connotes sophistication or cleverness "elicited the information by artful questioning". slick emphasizes smoothness and guile "slick operators selling time-sharing".