口くちが裂さけても言いえない

expression, i-adjective

wouldn't say it even if my mouth were torn apart; I would never say that

A strong idiomatic expression meaning one absolutely refuses to say something, no matter what. Often used when the speaker feels the statement is too embarrassing, shameful, or secret to utter.

• 彼かれの秘ひ密みつは口くちが裂さけても言いえない。

  I would never tell his secret, no matter what.

• 口くちが裂さけても言いえないけど、実じつはすごく後こう悔かいしている。

  I would never say it out loud, but actually I regret it deeply.