1. If you have a fat mouth, you talk too much, especially about things that should be secret.
2. Someone that's very talkative, especially when boastful.
3. One that informs, especially against another/others.
4. Someone who talks too loud and boastful; whoride.
That chick's a fat mouth! Don't tell her anything!
someone who runs their mouth and talks all the time.
you wouldnt want to tell them anything, because they are likely to tell the world.
watch your back around a fat mouth.
People named RJ tend to be a liar and a fat mouth.
1. the kind of person that talks crap and may have pathetic comebacks
2. someone who spreads rumors, even if they aren't true
3. that one person you can't tell your secrets to
Boy: You're a freak and you're ugly.
Girl: Kid, you need to back off and leave me the hell alone before I freaking punch you in your big, fat mouth.