unpredictability has 2 distinct synonyms spread across 2 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is predictability.
the quality of being guided by sudden unpredictable impulses
the trait of being unpredictably irresolute
“the volatility of the market drove many investors away”
Synonyms, antonyms and the broader and narrower relations for unpredictability come from Princeton University’s WordNet. Full sources and licences.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
lacking predictability