Generally taken to be another name for a homeless alcoholic. Some might say that the name is more specific than that. It implies someone who drinks cheap fortified wine such as Mad Dog 20/20, wears gloves with the fingers snipped off and huddles around fires started in trash cans on skid rows all over America. If one want's to be a hopeless romantic, one could assume that a wino was privy to some kind of special wisdom imparted by living so close to the edge of civilization and spending so much time in a mentally disorganized state, but that is probably not true.