expression, godan verb (-ru)
incur divine punishment; get into trouble for speaking ill
Idiomatic expression: literally 'one's mouth becomes warped', used to warn that speaking badly of others will bring misfortune or divine retribution. Often used in admonitions.
人の悪口を言うと口が曲がるよ。
If you speak ill of others, you'll get into trouble.
expression, godan verb (-ru)
warp one's mouth; have a crooked mouth
Literal meaning: the mouth becomes physically distorted or twisted. Rarely used outside the idiomatic sense; may appear in descriptive or medical contexts.
事故の後、彼は口が曲がってしまった。
After the accident, his mouth became crooked.