sneak out 溜走；渐隐；淡出。
sneak v.偷偷地走，潜行；偷带，偷拿。告密；（尤指向老师）打小报告。

【例句】
I thought I'd sneak up on him (= move close to him without him seeing) and give him a surprise.
我打算趁他不注意悄悄走到他身边，吓他一跳。

She was always sneaking on other kids in the class.
她总是向老师打小报告，说班里其他孩子的坏话。