zip one’s lip字面意思：用拉链封住口；实际意思： 守口如瓶，一声不吭。

【例句】
No matter what happened, he would zip his lip.
无论出什么事，他都会一声不吭。

As for anything told to me in confidence, well, I zipped my lip.
至于私底下告诉我的任何事情，我会守口如瓶的。