An apocalypse is a literary genre in which a supernatural being reveals cosmic mysteries or the future to a human intermediary. The term "apocalypse" comes from the Greek word "apokálypsis," which means a revelation. In Jewish and Christian writings, an apocalypse is 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.

The Book of Revelation is the only apocalypse in the New Testament, but passages reflecting the genre are to be found in the gospels and in nearly all the genuine Pauline epistles. An apocalypse will often contain much eschatological material, but need not.

In popular usage, "apocalypse" has come to be used as a synonym for catastrophe or a very serious event resulting in great destruction and change. It can also refer to a prophetic revelation, especially concerning a cataclysm in which the forces of good permanently triumph over the forces of evil.

In summary, an apocalypse is a genre of literature that reveals cosmic mysteries or the future through a supernatural being to a human intermediary. It can also refer to a catastrophic event resulting in great destruction and change.