The (usually)
religious belief that the world will end (in the
Final Judgement sense not the kaboom sense) on a multiple of the
thousandth year since the
birth of
Jesus Christ. Although the
exact year is the subject of
heated debate between
Millennialist
groups both
secular and
religious, most of the hardcore believers think that the
thousand year
reign of the
saints mentioned in
Revelations will begin on that
date.
The term comes from the Greek word for thousand, Chiliiad.