4
unprompted(adjective, simple, natural, casual, impulsive)
3
extemporary(adjective, free, casual, impulsive, spontaneous)
3
extemporized(adjective, informal, spontaneous, unprepared, unrehearsed)
3
fluky(adjective, chance, casual, random, haphazard)
3
hurried(adjective, impulsive, rash, unthinking)
3
instinctive(noun, adjective, simple, natural, casual)
3
natural(adjective, simple, casual, impulsive, willing)
3
reckless(noun, adjective, impulsive, rash, unthinking)
3
unannounced
3
unarranged(adjective, spontaneous, unprepared, unrehearsed, unpremeditated)
3
unaware(adjective, unqualified, unknowing, unsuspecting, unready)
3
uncalculated(adjective, chance, unintentional, accidental, unintended)
2
arbitrary
2
automatic(adjective, free, simple, fake, natural)
2
designless(adjective, insignificant, casual, irregular, senseless)
2
free(adjective, simple, fake, natural, casual)
2
headlong(noun, adjective, impulsive, rash, unthinking)
2
incognizant(unknowing, unaware, unsuspecting)
2
informal(adjective, free, casual, impulsive, unprepared)
2
naturally
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APASmart Define. (2015). unplanned thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/unplanned/thesaurus/synonyms
ChicagoSmart Define. 2015. "unplanned thesaurus" https://smartdefine.org/unplanned/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, unplanned thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/unplanned/thesaurus/synonyms>.
MLASmart Define. "unplanned thesaurus" 10 April 2015. Web. 25 September 2026. <https://smartdefine.org/unplanned/thesaurus/synonyms>