He sneaked out to the party when his parents weren't looking.

sneaked out 是动词短语 sneak out 的过去式形式。 sneak 意思是"偷偷移动、潜行"，out 表示"向外"。 sneak out 合起来表示"偷偷溜出去"，常指未经允许或不被发现地离开某个地方。