悪口惡 Kanji
私は彼が私の悪口を言っているところを押さえた。 I caught him speaking ill of me.
悪口雑言 Kanji
これだけ悪口雑言を浴びせられれば、後は怖いものなどありゃしない。かえってすっきりするよ。 I'm not afraid of anything after having verbal abuse heaped on me like that. In fact, I feel empowered by it.
陰悪口言 Kanji
人の陰で悪口を言うな。 Don't speak ill of others behind their back.