knowing

an expression in the eyes that shows you know or understand something that is not being said aloud.

a subtle smile indicating that you know something others don't.

a quick look that shows a shared secret or understanding between two people.

a movement of the head up and down to show agreement or understanding of a secret situation.

a wide, often amused smile that shows a shared secret or private joke.

quickly closing and opening one eye as a signal of a shared secret or private joke.

a smug or self-satisfied smile that shows you know a secret, often in a slightly unpleasant way.