Eat a rag
A ridiculous insult that people use when they're either being mean or just trying to be funny. It's like the dumbest way to get back at someone.
My teacher said 'Eat a rag' because I drew a mustache on the principal's face.
My cousin said 'Eat a rag' because I ate all the pizza.
My friend said 'Eat a rag' because I won the video game battle.