The Collaborative International Dictionary of English v.0.48:

Desolation \Des`o*la"tion\, n. [F. d['e]solation, L. desolatio.]
   1. The act of desolating or laying waste; destruction of
      inhabitants; depopulation.
      [1913 Webster]

            Unto the end of the war desolations are determined.
                                                  --Dan. ix. 26.
      [1913 Webster]

   2. The state of being desolated or laid waste; ruin;
      solitariness; destitution; gloominess.
      [1913 Webster]

            You would have sold your king to slaughter, . . .
            And his whole kingdom into desolation. --Shak.
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   3. A place or country wasted and forsaken.
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            How is Babylon become a desolation!   --Jer. l. 23.

   Syn: Waste; ruin; destruction; havoc; devastation; ravage;
        sadness; destitution; melancholy; gloom; gloominess.
        [1913 Webster]

WordNet (r) 3.0 (2006):

desolation
    n 1: the state of being decayed or destroyed [syn:
         devastation, desolation]
    2: a bleak and desolate atmosphere; "the nakedness of the
       landscape" [syn: bleakness, desolation, bareness,
       nakedness]
    3: sadness resulting from being forsaken or abandoned [syn:
       forlornness, loneliness, desolation]
    4: an event that results in total destruction [syn:
       devastation, desolation]