A slang term used to refer to an individual suspected of possessing an IQ at,near, or below the legal minimum of 70 which defines mental retardation (1.A. See downsyndrome). The term itself generally is reserved for one who has made an art out of reckless if not moronic behavior, to the point where it defines that person.
Note- To those unfamiliar with this condition, exposure to a minimal number of 'events' involving those afflicted with downstrome will generally trigger a reaction of sympathy and pity. Prolonged exposure will more than likely lead to illwill if not sudden gladiatorial attacks against those afflicted.
"Whoa, Ted's downstrome was flaring today. I think that motherfucker's off his meds."
"I think Brandon was kicked in the head by a horse or something, that guy's had serious fuckin' downstrome ever since I met him."