adv.狡猾的；秘密地；頑皮地

He's been drinking whiskey on the sly for thirty years. 他暗中偷喝威士忌酒已有三十年了。

Don't trust him, he is a sly old fox. 別相信他，他像老狐貍一樣狡猾。

Many people attended the meeting on the sly. 許多人秘密地參加了會議。

He was lurking slyly in the background. 他狡猾地躲在背後活動。

That sly girl managed to get her friend's job. 那個詭詐的女孩設法取得她朋友的工作。