Definition of sly in English:



  • 1Having or showing a cunning and deceitful nature.

    ‘a sly, manipulative woman’
    • ‘If the character feels angry, I go crazy; and it's the same with sadness, but with the Marquise, she is sly and calculating and that's my hardest challenge.’
    • ‘I'm starting to go faster at each race but I'm still not sly enough when it comes to hitting my adversaries!’
    • ‘She'd obviously met a bad bunch, for McCabe is immoral, deceitful and sly.’
    • ‘The dialogue is often artful, with sly suggestions that the seeds of various Shakespearean plots and themes were sown in the muck of their messy affair.’
    • ‘When Chinese describe a person as ‘a monkey’, it means the person is extremely sly or cunning.’
    • ‘Those raised in urban Western understanding of the psychology of the animal kingdom tend to view the fox as a cunning, sly, deceitful animal.’
    • ‘Lord knows the girl had made enough sly remarks about them getting together.’
    • ‘She was a rather cunning and sly teenager by nature, accented by her narrow brown eyes and usual smirk.’
    • ‘These bungalows had their own world, their own parties and picnics, their special sly and subtle ‘in’ jokes.’
    • ‘It's not impossible that such a conspiracy is taking place, because there are many sly people who manipulate the dumb citizens for their own benefit.’
    • ‘His character is a blending of many different traits: he's smart, sly, manipulative, dangerous, and much more.’
    • ‘It is sly, clever after a fashion, and undeniably effective.’
    • ‘Ray was oblivious to my cunning and sly plan, and I kept it that way.’
    • ‘The Romans, who will resolutely overwhelm an adversary with the might of arms, they say Phoenicians are deceitful and sly.’
    • ‘Diplomacy as a game values the sly, the cunning, the underhanded, the crafty.’
    • ‘But it is dispensed with such style, coupled to such a mixture of absurd silliness and sly knowingness about human nature, that you can't help falling for its charms.’
    • ‘How could he have forgotten how sly and deceitful Viya was?’
    • ‘Her letters therefore reveal a web of motives and sly manipulation that her uncomfortable position encouraged.’
    • ‘He was cunning, sly and a good strategist, beating her at games of wits when others can't.’
    cunning, crafty, clever, wily, artful, guileful, tricky, conniving, scheming, devious, designing, deceitful, duplicitous, dishonest, disingenuous, underhand, sneaky, untrustworthy
    View synonyms
    1. 1.1 Showing in an insinuating way that one has some secret knowledge that may be harmful or embarrassing.
      ‘he gave a sly grin’
      • ‘The sly grin on his face and the glint in Len's eyes said it all.’
      • ‘Galloway asked them, with a sly grin, to look out for his car.’
      • ‘He used to peel down to his jockstrap, muscles glistening, sly grin flashing, while firing cryptic answers at the media, which he loathed.’
      • ‘Given his reluctance to admit the obvious, it's no surprise he still manages to aim a selection of sly digs at the Australian umpires and authorities.’
      • ‘His early morning frown slowly turned into a sly, cheeky grin, as if to say, ‘Look what I've found.’’
      • ‘‘Something for you to eat,’ replies the breakfast girl with a sly grin.’
      • ‘At the Chelsea Flower Show, Ann-Marie Powell finds garden designers looking to a geometric future and enjoys japesters taking a sly dig at the past’
      • ‘He seems touched but then can't resist having a sly dig at himself by pointing out that the really tender thing to have done would have been not to include it on the album.’
      • ‘But that short eyebrow, sly grin and crooked jaw are now what make me, well, me.’
      • ‘‘We may let in a few goals,’ he said with a sly grin.’
      • ‘Was voting for these awards a sly dig at the American establishment?’
      • ‘By delivering her message with a sly grin, West reminded us that sex - and, by extension, life - is supposed to be fun.’
      • ‘The entire nation tuned in to watch his presentation of the 1994-1995 budget interspersed with Urdu couplets and sly digs at the opposition.’
      • ‘On the cover shot, Fleck sports a sly grin as if he knew what a wonderful journey he was about to embark on.’
      • ‘A sly, mischievous grin then appeared on the thief's face.’
      • ‘His hair will be carefully dishevelled (by me), he will be unshaven, and he will wear a sly grin.’
      • ‘He couldn't resist what appeared a sly dig at the directors of Dundee, suggesting that by refusing to accept his offer to invest, they were willing to risk their club's financial well-being.’
      • ‘Stan nodded conspiratorially, a sly grin creeping over his face.’
      • ‘Oozing grace, charm, wit and style, she gives a masterclass of the English mannered style - a raised eyebrow here or a sly grin there sufficient to keep us engaged.’
      • ‘Juliano would turn around and there would be Petty, looking at him with a sly grin that said, ‘I got you again.’’
      roguish, mischievous, impish, puckish, playful, teasing, naughty, wicked, waggish
      View synonyms
    2. 1.2 (of an action) surreptitious.
      ‘a sly sip of water’
      • ‘Nelson took a sip of the wine and a sly smile appeared.’
      surreptitious, furtive, stealthy, covert, secret
      View synonyms


  • on the sly

    • In a secretive fashion.

      ‘she was drinking on the sly’
      • ‘Cyclists take tows on the sly, grab drinks and food from them, and are paced back to the pack by them.’
      • ‘In truth, most of those same execs were having the movies in question transferred to tape so they could watch them in their homes or offices, and those transfers were getting duped on the sly and traded for other movies.’
      • ‘Still, it didn't stop youngsters from smuggling comic books among their school texts, and reading them on the sly, sometimes in class where the subject was boring, or when the teacher was an uninspiring type.’
      • ‘During examination time, it is common to hear parental lamentations about children abandoning their books and watching TV on the sly, whenever the elders are not around to keep a watchful eye.’
      • ‘The king's wife finds out his secret, and on the sly sends for the two children in the king's name.’
      • ‘He said: ‘The people around here have not had a chance to say anything, it has been done completely on the sly.’’
      • ‘And there still is such a thing as scavenging on the sly - sneaking into dumpsters for the great find.’
      • ‘Younger and wirier than his charge, talking a mile a minute and singing during his chores, he nonetheless shows a careworn, weary face, and he drinks on the sly.’
      • ‘They couldn't, and there was no way they could force the towns with ‘superior’ state law or, well, bribe over half the town population on the sly.’
      • ‘Unfortunately, the train to my conference left at 4 AM after a night spent trying to acquire a travel visa on the sly, which meant drinking a lot of vodka.’
      in secret, secretly, furtively, stealthily, sneakily, slyly, surreptitiously, covertly, clandestinely, on the quiet, on the side, behind someone's back, under cover
      View synonyms


Middle English (also in the sense ‘dexterous’): from Old Norse slœgr ‘cunning’, originally ‘able to strike’ from the verb slá; compare with sleight.