disaster

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

• noun An occurrence causing widespread destruction and distress; a catastrophe.
• noun A grave misfortune.
• noun Informal A total failure.
• noun Obsolete An evil influence of a star or planet.

from The Century Dictionary.

• To blast by the stroke of an unlucky planet. Spenser.
• To injure; afflict.
• To blemish; disfigure.
• noun . An unfavorable aspect of a star or planet; an ill portent; a blast or stroke of an unfavorable planet.
• noun Misfortune; mishap; calamity; any unfortunate event; especially, a sudden or great misfortune: a word used with much latitude, but most appropriately for some unforeseen event of a very distressing or overwhelming nature.
• noun Synonyms Calamity, Catastrophe, etc. (see misfortune); blow, stroke, reverse.

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

• noun obsolete An unpropitious or baleful aspect of a planet or star; malevolent influence of a heavenly body; hence, an ill portent.
• noun An adverse or unfortunate event, esp. a sudden and extraordinary misfortune; a calamity; a serious mishap.
• transitive verb obsolete To blast by the influence of a baleful star.
• transitive verb rare To bring harm upon; to injure.

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

• noun An unexpected natural or man-made catastrophe of substantial extent causing significant physical damage or destruction, loss of life or sometimes permanent change to the natural environment.
• noun An unforeseen event causing great loss, upset or unpleasantness of whatever kind.

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

• noun an event resulting in great loss and misfortune
• noun a state of extreme (usually irremediable) ruin and misfortune
• noun an act that has disastrous consequences