A 'gossip queen' is someone who enjoys talking about other people's lives. They are not very good at keeping secrets and enjoy sharing their opinions about others.
The expression is a combination of the words 'gossip' and 'queen'.
Gossip: a casual conversation about a person's private life that may be judgemental or untrue
Queen: a female ruler of an independent state
This is typically used to talk about women or girls, however, you could use the term 'gossip king' to describe a man.
