M.O.M.C.
M. O. M. C. means your mouth is going nonstop but your brain is on vacation. It’s what happens when you’re too dumb to shut up and too lazy to pay attention.
Guy at the gym: 'I’m gonna bench 300!' (He can’t even do 100.)
Girl in class: 'I’m the smartest person ever!' (She failed the test.)
Customer at the store: 'I want this, but I also want that, but I don’t want this anymore!'