improbability
  不大可能的事物,未必有之事
  Im·prob·a·bil·i·ty n.; pl. Improbabilities   The quality or state of being improbable; unlikelihood; also, that which is improbable; an improbable event or result.
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  improbability
       n : the quality of being improbable [syn: improbableness]
           [ant: probability]