An accidental wiping of the eyebrow during a bowl movement.
Usually occurs when someone has to expell a Massive Shit and a lot of sweating occurs. During the wipe, a finger mildly brazes the turd being wiped. Then, the person wipes his/her eyebrow to clear the sweat of a job well done, leaving a smear of fecal matter on the eyebrow or forehead. Thus, a BROWN BROW...
Jimmy had to unload a big one earlier. He must have not looked in the mirror because he didn't notice the brown brow he came out of the shitter with
Brown-brown is a form of powdered cocaine, cut with powder from gun cartridges. Commonly given to child soldiers in West African armed conflicts,1 the drug gained notoriety after it was used by Nicolas Cage's character, Yuri Orlov, in the 2005 film Lord of War