doing things in a secret and unfair way

a sneaky plan 偷偷摸摸的计划

used to describe something you do, eat, or drink especially when you do it without telling anyone or when you should not really do it

She snuck out for a sneaky cigarette. 她跑出去悄悄地抽了根烟。

There's always the temptation to take a sneaky peek at the presents under the Christmas tree. 去悄悄地偷看一眼放在圣诞树下的礼物是件诱人的事。