86 entries under willing topic. ×

39
natural(adjective, calm, open, simple, plain)
27
involuntary(noun, adjective, reasonable, common, ordinary)
25
automatic(adjective, free, fake, natural, casual)
24
impulsive(noun, adjective, moving, simple, easy)
19
instinctive(noun, adjective, simple, easy, natural)
17
unplanned(noun, adjective, free, fake, informal)
16
extemporaneous(noun, adjective, plain, impulsive)
15
impromptu(adjective, adverb, free, plain, impulsive)
15
voluntary(adjective, feature, characteristic, free, deliberate)
14
unprompted(adjective, plain, natural, thoughtless, impulsive)
13
unforced(adjective, feature, characteristic, simple, regard)
12
free(adjective, feature, characteristic, simple, fake)
11
offhand(noun, adjective, free, careless, casual)
11
gratuitous(adjective, feature, characteristic, free, deliberate)
11
unconstrained(adjective, feature, characteristic, free, simple)
10
extempore(adjective, free, simple, fake, informal)
10
unasked(adjective, feature, characteristic, free, regard)
10
unstudied(adjective, free, simple, easy, impulsive)
9
impetuous(noun, adjective, moving, passionate, violent)
9
improvised(adjective, free, impulsive, impulse)
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APASmart Define. (2015). spontaneous thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/spontaneous/thesaurus/synonyms
ChicagoSmart Define. 2015. "spontaneous thesaurus" https://smartdefine.org/spontaneous/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2015, spontaneous thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/spontaneous/thesaurus/synonyms>.
MLASmart Define. "spontaneous thesaurus" 3 August 2015. Web. 27 September 2026. <https://smartdefine.org/spontaneous/thesaurus/synonyms>