JMdict: 2134550

口が固い 【くちがかたい】

  1. [exp,adj-i] tight-lipped; able to keep a secret
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Kanji in this word:

Kanji Meanings On Readings Kun Readings Grade
口 Mouth コウ, ク くち 1
固 Harden, Set, Clot, Curdle コ かた.める, かた.まる, かた.まり, かた.い 4