short for "Drink Eachother's Dick Juice"
This happens when men are out doing manly things such as tailgating or camping and they have a communal cooler. As the day goes on, the men urinate, do not wash their hands and put their hands in the ice cooler, thus rinsing off their dick juice. As the day goes on, more and more dick juice ends up in the cooler water and finds itself on the moutpieces of the cans or bottles in the cooler.
Anyone drinking from the cooler is essentially drinking their Bro's dick juice.
Brad: Ya wanna drink some of my Natty Ice?
Jimmy: You read my mind. I'd love to dedj out.