'Improbability' definitions:

Definition of 'improbability'

From: WordNet
noun
The quality of being improbable; "impossibility should never be confused with improbability"; "the improbability of such rare coincidences" [syn: improbability, improbableness] [ant: probability]

Definition of 'Improbability'

From: GCIDE
  • Improbability \Im*prob`a*bil"i*ty\, n.; pl. Improbabilities. [Cf. F. improbabilit['e].] The quality or state of being improbable; unlikelihood; also, that which is improbable; an improbable event or result. [1913 Webster]

Synonyms of 'improbability'

From: Moby Thesaurus