This is a person who drinks heavily on a regular basis. Not your typical alcoholic or binge drinker. You will be able to tell if someone is a sloshbox if you sense that his binge drinking will last for about 25 years.
Someone who is more of an alcoholic than someone who is called Lushbag. A lushbag will eventually evolve in to a sloshbox.
A sloshbox will be on the floor before midnight, everynight.
I love this kid. He's a total sloshbox.
My sloshbox uncle left all of his beer cans on my front lawn.