Ar·ma·ged·don 
(är′mə-gĕdn)
(är′mə-gĕdn)n.
1.
a. Bible In the book of Revelation, the place of the gathering of armies for the final battle before the end of the world.
b. The battle involving these armies.
2. A decisive or catastrophic conflict.
[Late Latin Armagedōn, from Greek, from Hebrew har məgiddô, the mountain region of Megiddo : har, mountain; see hrr in the Appendix of Semitic roots + məgiddô, Megiddo.]