1.
gossip; talking negatively about someone behind their back
Speaking ill of someone when they are not present; malicious gossip.
I was deeply hurt when I found out people were gossiping about me behind my back.
陰口 combines 陰 (shadow, behind) and 口 (speech): saying bad things about someone where they cannot hear it.
Common expressions
- 陰口を言う / 叩く (to badmouth someone behind their back)
- 陰口を言われる / 叩かれる (to be talked about behind one's back)
- 陰口が多い (there is a lot of gossip)
The idiomatic verb is 叩く (literally "to hit"), which is at least as common as 言う here.
Similar words
- 悪口: badmouthing generally, whether to the person's face or not
- 噂: rumor or talk about someone, not necessarily negative
- 陰口 is specifically negative talk, and specifically out of earshot
Cultural note
陰口 is judged harshly because it damages group 和 (harmony) while giving the target no chance to answer. Being caught at it costs more social standing than the criticism itself would have.