3
free-willed(adjective, feature, characteristic, free, deliberate)
3
freely(adjective, feature, characteristic, free, deliberate)
3
genuine(adjective, feature, characteristic, honest, modest)
3
headlong(noun, adjective, thoughtless, rash, unthinking)
3
honorable(adjective, feature, characteristic)
3
honorary(adjective, feature, characteristic, free, regard)
3
honourable(adjective, feature, characteristic)
3
instant(adjective, prompt, emotional, instinctive, sudden)
3
off-the-cuff(adjective, simple, informal, natural, straightforward)
3
out of the blue(adjective, sudden)
3
quick(noun, adjective, passionate, violent, thoughtless)
3
unannounced(adjective, unexpected)
3
uncoerced
3
uncompensated(adjective, feature, characteristic, regard)
3
uncontrived(adjective, simple, easy, real, impulsive)
3
uninvited(adjective, willing, arrogant, unexpected, voluntary)
3
unpaid(adjective, feature, characteristic, free, deliberate)
3
unrequested(adjective, willing, arrogant, voluntary, unwelcome)
3
unrestrained(adjective, calm, simple, plain, relaxed)
3
unsought(adjective, willing, arrogant, voluntary, unwelcome)
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APASmart Define. (2015). spontaneous thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/spontaneous/thesaurus/synonyms
ChicagoSmart Define. 2015. "spontaneous thesaurus" https://smartdefine.org/spontaneous/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2015, spontaneous thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/spontaneous/thesaurus/synonyms>.
MLASmart Define. "spontaneous thesaurus" 3 August 2015. Web. 24 September 2026. <https://smartdefine.org/spontaneous/thesaurus/synonyms>