When you take a shit so huge that the tip of it pokes above the water and in spite of any effort to flush it, it just spins and remains in place like an ice berg.
Means to wait until the last possible minute to do a major assignment and then staying up all night (sometimes 2 nights) to finish. It then involves falling asleep in every class as a result; it is the pinnacle of procrastinatoryachievement.