Source : Webster's Revised Unabridged Dictionary (1913)

Ragnarok \Rag"na*rok"\, Ragnarok \Rag"na*r["o]k"\, n. [Icel.,
   fr. regin, r["o]gn, gods + r["o]k reason, origin, history;
   confused with ragna-r["o]kr the twilight of the gods.] (Norse
   Myth.)
   The so-called ``Twilight of the Gods'' (called in German
   {G["o]tterd["a]mmerung}), the final destruction of the world
   in the great conflict between the [AE]sir (gods) on the one
   hand, and on the other, the gaints and the powers of Hel
   under the leadership of Loki (who is escaped from bondage).

Ragnarok \Rag"na*rok"\, Ragnarok \Rag"na*r["o]k"\, n. [Icel.,
   fr. regin, r["o]gn, gods + r["o]k reason, origin, history;
   confused with ragna-r["o]kr the twilight of the gods.] (Norse
   Myth.)
   The so-called ``Twilight of the Gods'' (called in German
   {G["o]tterd["a]mmerung}), the final destruction of the world
   in the great conflict between the [AE]sir (gods) on the one
   hand, and on the other, the gaints and the powers of Hel
   under the leadership of Loki (who is escaped from bondage).

Source : WordNet®

Ragnarok
     n : myth about the ultimate destruction of the gods in a battle
         with evil [syn: {Gotterdammerung}, {Twilight of the Gods}]