Merriam-Webster Collegiate Dictionary - apocalypse

 noun  Etymology: Middle English, revelation, Revelation, from Anglo-French apocalipse, from Late Latin apocalypsis, from Greek apokalypsis, from apokalyptein to uncover, from apo- + kalyptein to cover — more at hell  Date: 13th century  1.  a. one of the Jewish and Christian writings of 200 B.C. to A.D. 150 marked by pseudonymity, symbolic imagery, and the expectation of an imminent cosmic cataclysm in which God destroys the ruling powers of evil and raises the righteous to life in a messianic kingdom  b. capitalized revelation 3  2.  a. something viewed as a prophetic revelation  b. Armageddon  3. a great disaster an environmental ~ APOCALYPSE  noun see revelation