Source : Webster's Revised Unabridged Dictionary (1913)

Tragedy \Trag"e*dy\, n.; pl. {Tragedies}. [OE. tragedie, OF.
   tragedie, F. trag['e]die, L. tragoedia, Gr. ?, fr. ? a tragic
   poet and singer, originally, a goat singer; ? a goat (perhaps
   akin to ? to gnaw, nibble, eat, and E. trout) + ? to sing;
   from the oldest tragedies being exhibited when a goat was
   sacrificed, or because a goat was the prize, or because the
   actors were clothed in goatskins. See {Ode}.]
   1. A dramatic poem, composed in elevated style, representing
      a signal action performed by some person or persons, and
      having a fatal issue; that species of drama which
      represents the sad or terrible phases of character and
      life.

            Tragedy is to say a certain storie, As olde bookes
            maken us memorie, Of him that stood in great
            prosperitee And is yfallen out of high degree Into
            misery and endeth wretchedly.         --Chaucer.

            All our tragedies are of kings and princes. --Jer.
                                                  Taylor.

            tragedy is poetry in its deepest earnest; comedy is
            poetry in unlimited jest.             --Coleridge.

   2. A fatal and mournful event; any event in which human lives
      are lost by human violence, more especially by
      unauthorized violence.

Source : WordNet®

tragedy
     n 1: an event resulting in great loss and misfortune; "the whole
          city was affected by the irremediable calamity"; "the
          earthquake was a disaster" [syn: {calamity}, {catastrophe},
           {disaster}, {cataclysm}]
     2: drama in which the protagonist is overcome by some superior
        force or circumstance; excites terror or pity [ant: {comedy}]