kapāla, (Sanskrit: “skull”), Tibetan thod pa, cup made of a human skull, frequently offered by worshipers to the fierce Tantric deities of Hindu India and Buddhist Tibet. In Tibet the skull cup is displayed on the Buddhist altar and is used in ritual to offer to the ferocious dharmapāla (“defender of the faith”) divinities either wine, which symbolizes blood, or dough cakes, which are shaped to resemble human eyes, ears, and tongues. The skull cup is often a handsomely worked object and rests on a triangular pedestal representing a sacrificial fire with skulls. The cup is mounted in metal, usually heavily embossed silver or gilt bronze, and topped with a lid shaped like half a skull, with a vajra- (“thunderbolt-”) shaped handle.
Source: http://www.britannica.com/EBchecked/topic/311715/kapala
