on the sly
adv. 秘密地
例句与用法：
Read it, if at all, on the sly, to look for their names.
(要看的话就偷偷地看，去找一找他们的名字。)
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。
She must have been having lessons on the sly.
她准是暗地里一直在上课。
Many people attended the meeting on the sly.
许多人秘密地参加了会议。
偷偷地
She is having an affair with her Japanese teacher on the sly.
她和她的日文老师偷偷有了恋情。
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。
When she thought no one was looking she opened the cupboard and took a few sweets on the sly.
当她觉得没人看见时, 她打开壁橱偷偷拿了几块糖。