IMPROBABILITY

n. quality of being unlikely to happen, unlikelihood; something which will probably not happen

Improbability may also refer to the opposite of probability. Improbability is the modal probability employed by Douglas Adams in The Hitchhiker's Guide to the Galaxy. Improbability is modeled after mathematical probability, but is only related to real probability in the sense that irony is related to chance. In the fiction of Douglas Adams, improbability is portrayed by a succession of increasingly unlikely events. As a literary device it is closer to the concept of deus ex machina than probability. However, as the characters frequently comment about how improbable this or that is, it becomes a point of self-reference.
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Noun
1. the quality of being improbable
(synonym) improbableness
(antonym) probability
(hypernym) uncertainty, uncertainness
(hyponym) unlikelihood, unlikeliness

(n.)
The quality or state of being improbable; unlikelihood; also, that which is improbable; an improbable event or result.
  

Synonyms and related words:
abnormality, anomaly, bare possibility, conversation piece, curio, curiosity, dark horse, exception, fighting chance, gambling chance, hardly a chance, hundred-to-one shot, inexpectance, inexpectancy, inexpectation, little chance, little opportunity, long odds, long shot, museum piece, no expectation, nonesuch, nonexpectation, oddity, off chance, outside chance, poor bet, poor lookout, poor possibility, poor prospect, prodigiosity, prodigy, rarity, remote possibility, slim chance, small chance, strange thing, the unforeseen, the unlooked-for, unanticipation, unexpectedness, unforeseeableness, unlikelihood, unpredictability, unpredictableness, unpreparedness, unreadiness