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English definition of “sly”

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adjective  /slɑɪ/ ( comparative slyer, superlative slyest) us  
not letting others know true opinions or intentions, or dishonest: She thought that by being sly, she could fool people. A cat can be a very sly animal.
adverb  /ˈslɑɪ·li/ us  
He winked slyly and lowered his voice, as if he had some secret to reveal.
(Definition of sly from the Cambridge Academic Content Dictionary © Cambridge University Press)
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