Strictly speaking, a theological term denoting a revelation or unveiling; in more popular use, a prediction of future crisis.
Apocalypticism is the religious belief that there will be an apocalypse, a term which originally referred to a revelation of God's will, but now usually refers to the belief that the end of the world is imminent, even within one's own lifetime. This belief is usually accompanied by the idea that civilization will soon come to a tumultuous end due to some sort of catastrophic global event.
Apocalypticism is often conjoined with the belief that esoteric knowledge that will likely be revealed in a major confrontation between good and evil forces, destined to change the course of history. Apocalypses can be viewed as good, evil, ambiguous or neutral, depending on the particular religion or belief system promoting them. They can appear as a personal or group tendency, an outlook or a perceptual frame of reference, or merely as expressions in a speaker's rhetorical style.