a. where someone who is full of shit, usually a homeschooled student, who has no social skills says stupid crap that makes you want to slap that person and ask them why they are so dumb. Cured by shutting the hell up.

b. a lapse of the brain, resulting in duh de duh. Otherwise referred to as a JT moment.
God, Kevin has diarrhea of the mouth. He just opens his face and stupid crap just sprays everywhere.
by Scottie does know December 14, 2005
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When you can not stop talking for nothing. When you just go on and on and on.
Mom caught me sneaking in last night. I started lying to her and I just had diarrhea of the mouth.

That lady had diarrhea of the mouth. She would just not shut up.
by Boobralicious July 20, 2009
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when you use a bunch of curse words, similar to Tourette's syndrome or when you spread a lot of gossip.
Guy: I can't believe you went out with that asshole. He is such a player!

Girl: At least I don't have diarrhea of the mouth!
by Jaeda June 15, 2008
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ONE WHO CANT SEEM TO KEEP HIS/HER MOUTH SHUT OR KEEP A SECRET TO SAVE HIS/HER LIFE!!
DID YOU HEAR ABOUT BETH GETTING AN STD FROM JOHN? YEH MICA AND HIS DIARRHEA MOUTH TOLD EVERYONE IN THE ENTIRE SCHOOL!!
by MARVELOUS INSANE CRAZY AMAZING November 11, 2008
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