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

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