He has to visit them on the sly.

他只得偷偷地去看望他们。

《牛津词典》

Under the cover of the smog, He snatched the pot on the sly.

在烟雾的掩护下，他偷偷地拿走了那只壶。

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He is orchestrating this sly but dramatic shift to civilize the fast-food experience.

FORBES: Marketing

Benjamin is a true star who brings understated and thoughtful sincerity to every line he speaks, Patton is sly and droll, and the entire cast (especially Terrence Howard, Faizon Love, and Ving Rhames) is a delight, but Bryan Barber directs with a music-video indiscipline, making shots with a casual profligacy and bathing them all in caramel light.

NEWYORKER: Idlewild

Mr. IVORY: The interesting thing about Sly is that when he left, he left.

NPR: Sly Stone Rumored to Make Grammy Bow