sly

Universal Words adjective 1 (disapproving) acting or done in a secret or dishonest way, often intending to trick people SYNCUNNING: a sly political move * (humorous) You sly old devil! How long have you known? 2 [usuallybeforenoun] suggesting that you know sth secret that other people do not know SYNKNOWING: a sly smile / grin / look / glance slyly adverb: He glanced at her slyly. slyness noun [U] IDIOMS on the sly secretly; not wanting other people to discover what you are doing: He has to visit them on the sly.