a person in or on a veichle, generally a motorbike, who is usually fat and has the momentum of a train. they are a danger to the roads or other riders as they are too uncoordinated and do not have the coordination to stop, therefore causing harm or death to other riders.
dirt biker 1: "hey man do you want to come riding"
dirt biker 2: "depends if jonny that death train is going or not"
dirt biker 1: "no way man, i'd never bring death train, not after that fat unbalanced, unco cunt
nearly killed me last time.
dirt biker 2: "sweet ill come then"