Door-hinge brain

A person with a Door-hinge brain is someone with a very low IQ, someone who is dumb to the point of being a laughing matter. The term comes from the fact that their brain is probably stuck to their skull using door-hinges, duct tape and nails.

Person 1 : "Dude he just ran face-first into a pole"
Person 2: "What a Door-hinge brain"