sly

adjective
1
acting or done in a secret or dishonest way, often intending to trick people
موذی, حیله‌گر, مکار, فریب‌کار
synonym cunning
2
suggesting that you know something secret that other people do not know
موذی, حیله‌گر, مکار, آب‌زیرکاه
a sly smile/grin
synonym knowing