unpredictable
[adjective]
Synonyms: inconstant, chance, changeable, doubtful, erratic, random, unforeseeable, unreliable, variable

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Antonyms: predictable

[TahlilGaran] English Synonym Dictionary ▲

un‧pre‧dict‧a‧ble AC /ˌʌnprɪˈdɪktəbəl◂/ adjective
[Word Family: noun: prediction, predictability ≠ unpredictability, predictor; adjective: predictable ≠ unpredictable, predictive; verb: predict; adverb: predictably ≠ unpredictably]

1. changing a lot so it is impossible to know what will happen:
unpredictable weather
the unpredictable nature of language

2. someone who is unpredictable tends to change their behaviour or ideas suddenly, so that you never know what they are going to do or think
—unpredictably adverb
—unpredictability /ˌʌnprɪdɪktəˈbɪləti, ˌʌnprɪdɪktəˈbɪlɪti/ noun [uncountable]

[TahlilGaran] Dictionary of Contemporary English ▲