The term commonly used to describe someone who talks behind other people's backs is "gossiper" or "gossipy."
- A "gossiper" is a noun that refers to a person who habitually spreads rumors or talks about others in a negative or sensationalized manner.
- "Gossipy" is the corresponding adjective used to describe someone who tends to engage in gossip or enjoys talking about others in a speculative or malicious way.
Both words imply a tendency to share information about others without their knowledge or consent, often involving private or sensitive details that may be harmful or damaging to the individuals being discussed. Gossiping can lead to strained relationships, hurt feelings, and a breakdown of trust among friends or acquaintances.