Ice is water that's gotten cold enough to freeze solid. When the pond in your neighborhood is solid ice in January, it's safe to skate on.
Ice takes many forms; you might slip on the ice, scrape sheets of ice off your car windows, or drop ice into your drink. In every case, the ice is frozen water, and when it freezes, it ices, the way roads ice over on winter nights. When you sprain your wrist, you should probably ice it, or hold ice on the injured area. You can also ice — or frost — a cupcake, or eat a sweet, cold fruit-flavored ice.