tragedy

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A drama or literary work in which the main character is brought to ruin or suffers extreme sorrow, especially as a consequence of a tragic flaw, moral weakness, or inability to cope with unfavorable circumstances.
• noun The genre made up of such works.
• noun The art or theory of writing or producing these works.
• noun A play, film, television program, or other narrative work that portrays or depicts calamitous events and has an unhappy but meaningful ending.
• noun A disastrous event, especially one involving distressing loss or injury to life.
• noun A tragic aspect or element.

from The Century Dictionary.

• noun A dramatic poem or composition representing an important event or series of events in the life of some person or persons, in which the diction is grave and dignified, the movement impressive and stately, and the catastrophe unhappy; that form of the drama which represents a somber or a pathetic character involved in a situation of extremity or desperation by the force of an unhappy passion.
• noun [capitalized] Tragedy personified, or the Muse of tragedy. See cut under Melpomene.
• noun A fatal event; a dreadful calamity.

from the GNU version of the Collaborative International Dictionary of English.

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

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A drama or similar work, in which the main character is brought to ruin or otherwise suffers the extreme consequences of some tragic flaw or weakness of character.
• noun The genre of such works, and the art of producing them.
• noun A disastrous event, especially one involving great loss of life or injury.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an event resulting in great loss and misfortune
• noun drama in which the protagonist is overcome by some superior force or circumstance; excites terror or pity