Sly1. (v. t.) Dexterous in performing an action, so as to escape notice; nimble; skillful; cautious; shrewd; knowing; -- in a good sense.
2. (v. t.) Artfully cunning; secretly mischievous; wily.
3. (v. t.) Done with, and marked by, artful and dexterous secrecy; subtle; as, a sly trick.
4. (v. t.) Light or delicate; slight; thin.
5. (adv.) Slyly.
Thesaurus Entries
Byzantine, Machiavellian, Machiavellic, acute, adroit, arch, artful, astute, back-door, backstairs, cagey, calculating, canny, clandestine, clever, covert, crafty, creep, crooked, cunning, cute, deceitful, deep, deep-laid, designing, devious, dexterous, diplomatic, dishonest, disingenuous, downy, feline, foxy, furtive, guileful, gumshoe, hidlings, hole-and-corner, hugger-mugger, ingenious, insidious, inventive, knowing, lurk, masterful, pawky, politic, predatory, privy, quiet, ready, resourceful, scheming, serpentine, shady, sharp, shifty, shrewd, skulk, skulking, slick, slide, slim, slink, slinking, slinky, slippery, smart, smooth, snake, snaky, sneaking, sneaky, snook, sophistical, steal, stealthy, strategic, subtile, subtle, supple, surreptitious, tactical, trickish, tricksy, tricky, under-the-counter, under-the-table, undercover, underground, underhand, underhanded, unfrank, unobtrusive, unscrupulous, vulpine, wary, wily