口くち無なし

noun

something unspoken; unspoken matter

Refers to things left unsaid, often with a nuance of something that should have been said or is deliberately not spoken. Used in phrases like 口無しの約束 (unspoken promise).

• 二人ふたりの間あいだには口くち無なしの了りょう解かいがあった。

  There was an unspoken understanding between the two of them.

noun

non-functional mouth; mouth that cannot speak

Describes a mouth that is physically unable to speak or is treated as if it cannot speak. Rare standalone use; more often seen in literary or metaphorical contexts.

• その人にん形ぎょうは口くち無なしの顔かおで、何なにも語かたらなかった。

  The doll had a mouthless face and said nothing.