n. pl. crateres (krā˙-tē′ rēz). In classical antiquity, a large vessel or vase in which water was mixed with wine according to accepted formulas, and from which it was dipped out and served to the guests in the smaller pouring-vessels (oinochoe).n. In geology, the cup-shaped depression or cavity of a volcano, forming the orifice through which the erupted material finds its way to the surface, or has done so in former times if the volcano is at present extinct or dormant.n. Milit., a cavity formed by the explosion of a military mine.n. Any hollow made in the earth by subterranean forces.n. [capitalized] An ancient southern constellation south of Leo and Virgo. It is supposed to represent a vase with two handles and a base.n. In electricity, a hollow cavity formed in the positive carbon of an arclamp when continuous currents are used.n. A caldera.