A slang phrase referring to nausea of such extreme intensity that the physical act of vomiting "feels" comparable to expelling the contents of your viscera or gray matter (brain).
If you drink too much alcohol, you'll be "puking your brains out" in front of everyone.
When something is boring, someone is talking about something no one cares about, or when someone is arguing for no reason. Or bitch just u need to shut up