The Collaborative International Dictionary of English v.0.48:

Disastrous \Dis*as"trous\, a. [Cf. F. d['e]sastreux. See
   Disaster.]
   1. Full of unpropitious stellar influences; unpropitious;
      ill-boding. [Obs.]
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            The moon
            In dim eclipse, disastrous twilight sheds. --Milton.
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   2. Attended with suffering or disaster; very unfortunate;
      calamitous; ill-fated; ending in utter failure or ruin;
      as, a disastrous day; a disastrous termination of an
      undertaking.
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            Wherein I spake of most disastrous chances. --Shak.
      -- Dis*as"trous*ly, adv. -- Dis*as"trous*ness, n.
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