Sudden Ice Shift Syndrome. An event that sometimes occurs when a person is drinking a beverage containing ice. As a container is tipped up to pour the liquid into the mouth, a mass of ice, formerly lodged near the bottom of the container, shifts under the force of gravity, causing the beverage to spill down the chin of the drinker. This phenominon is not observed when drinking through a straw.
As he mopped the stain on the front of his shirt, the young man who had just tried to pour the last of his long island iced tea into his mouth exclaimed "SISS!" (pronouncing the acronym S.I.S.S.)