Best definition
An illness caused by not hanging out with one’s bros for an extended period of time. Symptoms begin at 24 hours and include slight headaches and idly wondering what one’s bros are doing. These progress to severe headaches, a strong compulsion to see one’s bros, a desire to drink and, if left untreated, total organ failure. The only known cures are emergency bro time and the time honored cure-all of sucking it up.
Guy: What happened to him doc?

Doctor: Extreme case of withbrowal. All of his organs exploded.

Guy: What?