諱莫如深 [讳－－－]

Jyutping wai5 mok6 jyu4 sam1
Pinyin huì mò rú shēn

Definitions (CC-CEDICT)
  1. important matter that must be kept secret (idiom); don't breathe a word of it to anyone!
Definitions (Wiktionary)
  1. phrase, idiomatic
    to keep one's mouth shut about a secret to guard it closely
Definitions (Kaifangcidian)
  1. （沒有對應漢語詞彙）