1. General term for a circular, funnel-shaped depression, up to 1km in diameter, produced by volcanic processes by which gases, tephra, and lava are or have been ejected. Several types are recognized: a crater at the summit of a volcanic cone marks the site of magma degassing and ejection of material; a maar, often occupied by a lake, results from explosive activity; and a caldera is a large volcanic depression greater than 1 km in diameter.
2. Near-circular depression produced by the impact of an extraterrestrial body, e.g. Meteor Crater, Arizona. Meteorite craters are formed by the explosion outward and upward of material compressed and heated strongly by the energy of impact, and so usually are circular at the time they form. They are characterized by topographically raised rims and by ejecta blankets which show inverted stratigraphy with respect to the target rocks. See also SHATTER CONES.
cra·ter / ˈkrātər/ • n. 1. a large, bowl-shaped cavity in the ground or on the surface of a planet or the moon, typically one caused by an explosion or the impact of a meteorite or other celestial body. ∎ a large pit or hollow forming the mouth of a volcano. ∎ a cavity or hole in any surface.2. a large bowl used in ancient Greece for mixing wine.• v. [tr.] form a crater in (the ground or a planet): he has the offensive power to crater the enemy's runways.
Cra·ter / ˈkrātər/ Astron. a small and faint southern constellation (the Cup), between Hydra and Leo, said to represent the goblet of Apollo. ∎ [as genitive] (Cra·te·ris / krāˈti(ə)ris/ ) used with a preceding letter or numeral to designate a star in this constellation: the star Delta Crateris.