Gossip

"Gossip is when you hear something you like about someone you don't." - Earl Wilson
There few things that can really tear relationships or businesses apart like gossip.
You may work with a gossiper. You might even live with a gossiper.
My advice: get away from them. Whatever it takes, do not get caught up in their banter.
Whether they say "I need to vent" or "I have to get something off my chest" it's all the same. Gossip is gossip.
It's destructive and it's cowardly.
If you can't say it to that person's face then you have no business saying it behind their back.