- 1(disapproving) acting or done in a secret or dishonest way, often intending to trick people synonym cunning a sly political move (humorous) You sly old devil! How long have you known?
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- 2[usually before noun] suggesting that you know something secret that other people do not know synonym knowing a sly smile/grin/look/glance, etc. Idioms
secretly; not wanting other people to discover what you are doing He has to visit them on the sly.
adverb He glanced at her slyly.
noun [uncountable]See sly in the Oxford Advanced Learner's Dictionary
Check pronunciation: sly