The Collaborative International Dictionary of English v.0.48:

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.]
   [1913 Webster]
   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.
      [1913 Webster]

            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.
      [1913 Webster]

            All our tragedies are of kings and princes. --Jer.
                                                  Taylor.
      [1913 Webster]

            tragedy is poetry in its deepest earnest; comedy is
            poetry in unlimited jest.             --Coleridge.
      [1913 Webster]

   2. A fatal and mournful event; any event in which human lives
      are lost by human violence, more especially by
      unauthorized violence.
      [1913 Webster] Tragic

The Collaborative International Dictionary of English v.0.48:

Drama \Dra"ma\ (dr[aum]"m[.a] or dr[=a]"m[.a]; 277), n. [L.
   drama, Gr. dra^ma, fr. dra^n to do, act; cf. Lith. daryti.]
   1. A composition, in prose or poetry, accommodated to action,
      and intended to exhibit a picture of human life, or to
      depict a series of grave or humorous actions of more than
      ordinary interest, tending toward some striking result. It
      is commonly designed to be spoken and represented by
      actors on the stage.
      [1913 Webster]

            A divine pastoral drama in the Song of Solomon.
                                                  --Milton.
      [1913 Webster]

   2. A series of real events invested with a dramatic unity and
      interest. "The drama of war." --Thackeray.
      [1913 Webster]

            Westward the course of empire takes its way;
            The four first acts already past,
            A fifth shall close the drama with the day;
            Time's noblest offspring is the last. --Berkeley.
      [1913 Webster]

            The drama and contrivances of God's providence.
                                                  --Sharp.
      [1913 Webster]

   3. Dramatic composition and the literature pertaining to or
      illustrating it; dramatic literature.
      [1913 Webster]

   Note: The principal species of the drama are tragedy and
         comedy; inferior species are tragi-comedy,
         melodrama, operas, burlettas, and farces.
         [1913 Webster]

   The romantic drama, the kind of drama whose aim is to
      present a tale or history in scenes, and whose plays (like
      those of Shakespeare, Marlowe, and others) are stories
      told in dialogue by actors on the stage. --J. A. Symonds.
      Dramatic

WordNet (r) 3.0 (2006):

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, tragedy, cataclysm]
    2: drama in which the protagonist is overcome by some superior
       force or circumstance; excites terror or pity [ant: comedy]