"Apocalypsis" is a Greek word, ἀποκάλυψις, meaning revelation or unveiling. It refers to the revealing of divine mysteries, often involving otherworldly beings mediating a revelation to a human recipient. While commonly used to mean a catastrophe or the end of the world, the original meaning is more about uncovering hidden truths. In the context of the Book of Revelation, it signifies the unveiling of future events and a transcendent reality.