tragedy

n. dramatic composition with an unhappy ending portraying a conflict between the protagonist and destiny or circumstances; literary creation in this form; disaster, calamity

In a figurative sense a tragedy (from Classical Greek τραγωδία, "song for the goat", see below) is any event with a sad and unfortunate outcome, but the term also applies specifically in Western culture to a form of drama defined by Aristotle characterized by seriousness and dignity and involving a great person who experiences a reversal of fortune (Peripeteia). (Aristotle's definition can include a change of fortune from bad to good as in the Eumenides, but he says that the change from good to bad as in Oedipus Rex is preferable because this effects pity and fear within an audience.) According to Aristotle, "The structure of the best tragedy should be one that represents for that is peculiar to this form of art." This reversal of fortune must be caused by the tragic hero's hamartia, which is often mistranslated as a character flaw, but is more correctly translated as a mistake (since the original Greek etymology traces back to hamartanein which is a sporting term which refers to an archer or spear-thrower missing his target). According to Aristotle, "The change to bad fortune which he undergoes in not due to any moral defect or flaw, but a mistake of some kind." It is also a misconception that this reversal can be brought about by a higher power (e.g. the law, the gods, fate, or society), but if a character’s downfall is brought about by an external cause Aristotle describes this as a "misadventure" and not a tragedy.
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Noun
1. an event resulting in great loss and misfortune; "the whole city was affected by the irremediable calamity"; "the earthquake was a disaster"
(synonym) calamity, catastrophe, disaster, cataclysm
(hypernym) misfortune, bad luck
(hyponym) act of God, force majeure, vis major, inevitable accident, unavoidable casualty
2. drama in which the protagonist is overcome by some superior force or circumstance; excites terror or pity
(antonym) comedy
(hypernym) drama
(hyponym) tragicomedy

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

(n.)
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.
  

To dream of a tragedy, foretells misunderstandings and grievious disappointments. To dream that you are implicated in a tragedy, portends that a calamity will plunge you into sorrow and peril.