A term referring to a syndrome held by an insecure and extremely emotional girl who keeps opening her mouth to try to solve her personal and relationship issues by talking about them at the wrong time and to the wrong people, even after her guy told her continuously that it was making these issues worse. She keeps doing it over and over despite the fact that drama keeps happening because of her gargantuan mouth flapping. Over time the syndrome gets worse and worse. It finally climaxes over a couple of weeks because of some really horrendous incidents caused by her jabberjawing. So the girl finally breaks down one day after betraying his trust yet again, and she signs up for therapy to try to work on her self-control issues and her listening skills. Although she hopes her guy will trust her once again and give her a chance to share their love and happiness together once more like they did when she was his bear (really misses that), she'll be okay either way. Even if the changes she has made don't bring him back to her, she will be a stronger and happier person in the end because she won't ever hurt anybody like that again. She will defeat the Big Mouth Syndrome.
Melissa knew she had the big mouth syndrome when she asked her boyfriend's friend for advice during a very panicky moment, even though she knew he would be pissed if he found out.