knowing
adj.adj. showing that you know a secret or understand something that is not being said out loud. You use this to describe a look or a smile that suggests you are 'in on the joke'.
adj. suggesting possession of secret or inside information; showing a sophisticated or shrewd awareness of a situation. Often used to describe facial expressions or gestures that imply a shared understanding between people.
She gave me a knowing smile across the dinner table.
The two colleagues exchanged a knowing look when the boss mentioned the 'surprise' office party.
The author peppers the narrative with knowing references to local history, rewarding long-time residents while keeping the core plot accessible to newcomers.
From know + -ing.
Typically used as an attributive adjective before a noun like 'smile', 'look', or 'glance'.