Synonyms for Unpredictable (same or very similar meaning)
WordNet sense 1 (changeable):
capricious
WordNet sense 2 (not capable of being definitely decided or ascertained):
indeterminable, undeterminable
WordNet sense 3 (not occurring at expected times):
irregular
WordNet sense 4 (recurring in scattered and irregular or unpredictable instances):
sporadic
From the ODE community, based on WordNet
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