The Collaborative International Dictionary of English v.0.48:

Disaster \Dis*as"ter\, n. [F. d['e]sastre; pref. d['e]s- (L.
   dis-) + astre star, fr. L. astrum; a word of astrological
   origin. See Aster, Astral, Star.]
   1. An unpropitious or baleful aspect of a planet or star;
      malevolent influence of a heavenly body; hence, an ill
      portent. [Obs.]
      [1913 Webster]

            Disasters in the sun.                 --Shak.
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   2. An adverse or unfortunate event, esp. a sudden and
      extraordinary misfortune; a calamity; a serious mishap.
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            But noble souls, through dust and heat,
            Rise from disaster and defeat
            The stronger.                         --Longfellow.

   Syn: Calamity; misfortune; mishap; mischance; visitation;
        misadventure; ill luck. See Calamity.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Disaster \Dis*as"ter\, v. t.
   1. To blast by the influence of a baleful star. [Obs.] --Sir
      P. Sidney.
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   2. To bring harm upon; to injure. [R.] --Thomson.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disaster
    n 1: a state of extreme (usually irremediable) ruin and
         misfortune; "lack of funds has resulted in a catastrophe
         for our school system"; "his policies were a disaster"
         [syn: catastrophe, disaster]
    2: 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]
    3: an act that has disastrous consequences