A phrase uttered in such rage that telling another human being to suck a dick would not convey the full intent of the speaker. Generally used sarcastically in return to blatant sarcasm, resulting in a perpetual cycle of bag-eating.
Commonly abbreviated as "eat a bag" or simply "a bag."
When someone has an attitude or is hella worked up and needs to calm the f**k down. A reference to the Snickers commercials when someone "is not themself" until they eat a Snickers.