1
malicious gossip;backbiting;speaking ill behind someone's back
だれか人に、言い分があったら、陰口をいわないで、その人に面と向かっていいなさい。
If you have a bone to pick with a person, tell it to his face instead of saying things behind his back.
Other forms
蔭口 【かげぐち】 (search-only kanji form) · 影口 【かげぐち】 (search-only kanji form)