7
unconscious(adjective, simple, natural, casual, impulsive)
6
ad hoc(expression, adjective, idiom, free, unplanned)
6
ad libitum(expression, adjective, idiom, adverb, informal)
6
extemporaneously(adverb, impulse, offhand, spontaneously, improv)
6
extemporization(noun, planned, prepared, improvised, improvisation)
6
haphazard(adjective, unprepared, accidental, unintended)
6
hasty(adjective, impulsive)
6
improvisation(noun, planned, impulse, prepared, improvised)
5
offhanded
5
candid
5
extemporized(adjective, adverb, informal, unprepared, unplanned)
5
improv(adjective, adverb, free, offhand, unprepared)
5
improvise(verb, adjective, informal, unplanned, extemporize)
5
impulsive(adjective, adverb, simple, natural, chance)
4
abrupt(adjective, impulsive)
4
automatic(adjective, free, simple, fake, natural)
4
informal(adjective, free, casual, impulsive, spontaneous)
4
involuntary(adjective, simple, natural, casual, impulsive)
4
reflex
4
snap(adjective, free, casual, impulsive, prepared)
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APASmart Define. (2016). impromptu thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/impromptu/thesaurus/synonyms
ChicagoSmart Define. 2016. "impromptu thesaurus" https://smartdefine.org/impromptu/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2016, impromptu thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/impromptu/thesaurus/synonyms>.
MLASmart Define. "impromptu thesaurus" 28 January 2016. Web. 20 September 2026. <https://smartdefine.org/impromptu/thesaurus/synonyms>