Do something on the sly

Definition: do something without having other people notice

定义：秘密地做某事。

She did it on the sly. Her husband never had a clue.

她偷偷地做这件事，她丈夫绝不会有线索。

He made lots of money by doing it on the sly.

他偷偷地挣了很多钱。