sly
adj. B2 Upper Intermediate US //ˈsɫaɪ// UK //slˈaɪ// sly
adj. acting in a clever but dishonest way to get what you want. You use this to describe someone who is good at keeping secrets or tricking others.
adj. showing a cunning or deceitful nature; skilled at achieving goals through indirect or underhanded means. Often implies a playful or knowing quality when describing a look or remark.
He gave me a sly smile before he left.
The fox is often portrayed as a sly character who outsmarts the other animals in the forest.
Her sly suggestion that the project might face delays was a calculated move to undermine her rival's confidence without making a direct accusation.
Usage
Commonly used to modify nouns like 'smile', 'look', or 'glance' to indicate shared, secret knowledge.