sly(redirected from on the sly)
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Related to on the sly: get on, fall apart, catch up, stay put, turn up, called off
slyadjective arch, artful, astute, astutus, calculating, clandestine, conniving, covert, covinous, crafty, crooked, cunning, deceitful, deceiving, deceptious, deceptive, delusive, designing, devious, dishonest, dishonorable, disingeuous, double-dealing, evasive, feline, foxy, furtive, guileful, hidden, insidious, intriguing, keen, obreptitious, plotting, scheming, secret, secretive, sharp, shifty, shrewd, skulking, slippery, sneaking, sneaky, stealthy, subdolus, subtle, surreptitious, treacherous, tricky, uncandid, underhand, underhanded, unscrupulous, vafer, vulpine, wily
See also: artful, covert, deceptive, devious, disingenuous, furtive, insidious, machiavellian, mendacious, secret, stealthy, subtle, unscrupulous