4
not predicted(expression, adverb, unpredictable, surprising, unanticipated)
4
rash(adjective, sudden, unlooked-for, unhoped)
4
rushing(adjective, sudden, unlooked-for, unhoped)
4
spontaneous(adjective, sudden, unlooked-for, unhoped)
4
surprising(adjective, adverb, surprise, unexpected, unpredicted)
4
unexpectedly(adjective, adverb, unpredictable, surprising, subitaneous)
4
unplanned(adjective, adverb, surprise, unexpected, unprepared)
4
unprepared for(expression, adverb, unpredictable, surprising, unanticipated)
4
urgent(adjective, sudden, unlooked-for, unhoped)
4
without warning(expression, adjective, extraordinary, wonderful, surprise)
3
acute(adjective, sudden, unlooked-for, unhoped)
3
instant(adjective, sudden, unlooked-for, unhoped)
3
flashing(adjective, sudden, unlooked-for, unhoped)
3
fleeting(adjective, sudden, unlooked-for, unhoped)
3
instantaneous(adjective, sudden, unlooked-for, unhoped)
3
quickening(adjective, sudden, unlooked-for, unhoped)
3
reckless(adjective, sudden, unlooked-for, unhoped)
3
rushed(adjective, sudden, unlooked-for, unhoped)
3
sharp(adjective, sudden, unlooked-for, unhoped)
3
speedy(adjective, unpredictable, surprising, subitaneous)
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APASmart Define. (2015). out of the blue thesaurus. Retrieved September 29, 2026, from https://smartdefine.org/out_of_the_blue/thesaurus/synonyms
ChicagoSmart Define. 2015. "out of the blue thesaurus" https://smartdefine.org/out_of_the_blue/thesaurus/synonyms (accessed September 29, 2026).
HarvardSmart Define 2015, out of the blue thesaurus, Smart Define, viewed 29 September, 2026, <https://smartdefine.org/out_of_the_blue/thesaurus/synonyms>.
MLASmart Define. "out of the blue thesaurus" 3 August 2015. Web. 29 September 2026. <https://smartdefine.org/out_of_the_blue/thesaurus/synonyms>