“三缄其口”，是一个汉语成语，意思是沉默不谈，像瓶口塞紧了一般（keep one's mouth shut as that of a jar）。比方说话慎重，严守隐秘，能够翻译为“seal one's lips”，或“ be tight-mouthed”。
例句：
他对她的身份三缄其口。
He closely guarded her identity.
不管出什么事，他都会三缄其口。
No matter what happened, he would not say a word.
约翰有意说出来，但玛丽要他三缄其口。
John wanted to talk, but Mary told him to keep his lips buttoned.
