守ㄕㄡˇ口ㄎㄡˇ如ㄖㄨˊ瓶ㄆㄧㄥˊshǒukǒu‑rúpíng

  1. 嘴巴像瓶口塞緊了一般。比喻說話謹慎，嚴守祕密。也作「緘口如瓶」。例 「這件事請守口如瓶，不可對人提起」。

英lit. to guard one's mouth like a closed bottle (idiom)​; tight-lipped, reticent, not breathing a word
德Geheimhaltung (S)​