secretly; in a sneaky way
en secret; de manière rusée (en secret; de manière rusée)
"He met her on the sly without telling anyone."
"Il l'a rencontrée en secret sans le dire à personne." (Il l'a rencontrée **en secret** sans le dire à personne.)
to set a firm boundary or make a limit clear
A source of continuous profit or success.
creative and different from usual ideas
stay calm; don’t get angry or impatient
a casual way to admit a small mistake
unable to think clearly or remember something