Stands for Morning After Dump. This is the dump taken the next morning after a long night of drinking, when the endless pints of barley and hops have temporarily morphed your intestines and colon into a gassy, volatile mass of crap. It is characterized by copious amounts of loud farting, occasional spurts of runniness, and a god awful smell reminiscent of swamp water, rotting cabbage, and gangrene. It is best taken with others present so that they may bask in the toxic stench, gasping for fresh air and screaming for mercy, all the while as you sit patiently, scouring your memory in order to piece together the events from the previous evening while you simultaneously empty your putrid innards into the porcelain goddess.
Guy 1: "Good God in Heaven, what is that smell? Did someone use chemical weaponry in our house?!"
Guy 2 (from bathroom): "Sorry dude, had to drop the MAD, I thought I was going to crap myself. I have plenty of Fabreeze, don't worry."
Guy 1: "Fabreeze?! We'll need a friggin' priest to get that disgusting stench out of here!!"