1. A referenced to a prophetic of devastation or ultimate doom.
2. Warning about a disastrous future or outcome: "We hear more and more about the apocalyptic warnings of global warming."
3. Involving a description of a widespread destruction and devastation.
4. A reference to the predicting of, or presaging of, an imminent disaster and total or universal destruction: "Apocalyptic teachings or writings; or specifically, apocalyptic literature."

A class of Jewish and Christian writings beginning about 250 B.C. and continuing into the opening centuries of A.D.

Their purpose was to comfort the faithful in their suffering conditions, and reconcile those conditions with God's righteousness by prefiguring the future triumph of Israel or the Messianic kingdom.

The best-known Christian apocalypse is the Book of Revelation in the New Testament of the Bible.

The number 666, applied to the Beast in the book of Revelation, chapter 13, verse 18 of the New Testament of the Bible.

"Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six."

"This calls for wisdom: let him who has understanding reckon the number of the beast, for it is a human number, its number is six hundred sixty-six."