al-Dajjal ("The Deceiver/impostor" ) is an evil figure in Islamic eschatology, who will appear before Yawm al-Qiyamah (Resurrestion Day). He is similar to the Antichrist in Christianity
"Dajjal" is a common Arabic word, used in the sense of "false prophet". But "Al-Dajjal", with the definite article, refers to "The Impostor", a specific end-of time deceiver. It is worthy to note that the term Al-Masih Ad-Dajjal (Arabic for "The False Messiah" ) is a literal translation of the Syriac term "Meshiha Deghala", which had been in the common vocabulary of the Middle East for more than 400 years prior to the Quran via the Peshitta (which uses that term instead of the Greek "antichristos" ).
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http://en.wikipedia.org/wiki/Dajjal