Definition: Blabbermouth is a slang term used to describe someone who talks too much or reveals secrets or private information without thinking about the consequences.
Use case: You can use the term blabbermouth to describe someone who can't keep a secret or talks too much about things that should be kept private. For example, "I can't trust Sarah with my secrets because she's such a blabbermouth."
• That blabbermouth spilled the beans about our secret project to the whole office.
• My little brother is such a blabbermouth, he tells everyone about my personal life.
• She's such a blabbermouth, I told her not to tell anyone but she couldn't keep it a secret.
• I can't stand being around that blabbermouth, she talks so much and never knows when to stop.
• I heard that the new guy in accounting is a bit of a blabbermouth, so be careful what you say around him.
• Don't be a blabbermouth and tell anyone about our surprise party.