When you eat so much taco bell that you shit in your pants so bad that it forms a belt around your waist.
"Dan ate so many chalupas from taco bell that he'll end up with a taco belt later."
A taco belt is when you eat so much taco bell that you end up shitting your pants. At that point, it forms around your waste like a belt. Which is why its known as a "taco belt".
"Daniel ate so much Taco Bell that he might end up with a taco belt later."