1. a person who talks too much or reveals secrets
Usage: informal
2. a person who boasts or brags excessively
Usage: informal

Examples

• Don’t tell Sarah the surprise party details – she’s such a bigmouth.
• That bigmouth at work is always bragging about his salary.
• I can’t trust him with confidential information because he’s a bigmouth.
• The bigmouth in our group ruined the surprise by telling everyone.
• She called him a bigmouth after he revealed her personal business.
• Nobody likes working with a bigmouth who can’t keep things private.