Indicates someone's annoying habit of talking too much, not just chattiness. Don't let Marina join our plan, she's a loudmouth.
Pro Tip 2/3
Secret Spilling
Implies the person may reveal secrets or private information without discretion. I avoided telling Brian about the surprise party because he's a known loudmouth.
Pro Tip 3/3
Informal Usage
Used in casual conversations, may be rude in formal settings. Our coach is supportive but can be a loudmouth on the sidelines.