3
straightaway(adverb, straight, first, directly, immediately)
3
unexpectedly(adverb, suddenly, inexpectation)
2
all at once(expression, idiom, adverb, haste, instantaneity)
2
at short notice(expression, idiom, directly, immediately, rapidly)
2
away(directly, immediately, rapidly, instantly)
2
early(haste, instantaneity)
2
extempore(instantaneity, earliness)
2
fleetingly(adverb, transiently)
2
in a trice(expression, idiom, adverb, instantaneity)
2
in nothing flat(expression, idiom, directly, immediately, rapidly)
2
incontinently
2
just then(expression, idiom, instantaneity)
2
now(adverb, straight, directly, immediately, rapidly)
2
on the dot(expression, idiom, directly, immediately, rapidly)
2
on the instant(expression, idiom, earliness)
2
precipitously(adverb, suddenly)
2
straight off(verb, expression, adverb, phrasal verb, directly)
2
summarily(first, now, directly, immediately, rapidly)
2
thereupon(first, now, directly, immediately, rapidly)
2
this instant(expression, adverb, directly, immediately, rapidly)
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APASmart Define. (2015). instantaneously thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/instantaneously/thesaurus/synonyms
ChicagoSmart Define. 2015. "instantaneously thesaurus" https://smartdefine.org/instantaneously/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2015, instantaneously thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/instantaneously/thesaurus/synonyms>.
MLASmart Define. "instantaneously thesaurus" 14 April 2015. Web. 22 September 2026. <https://smartdefine.org/instantaneously/thesaurus/synonyms>