vacillate

/ˈvæ.sə.leɪt/

//ˈvæ.sə.leɪt// verb

"vacillate" is a 9-letter English headword indexed on PlainSpell.

The verdict

“vacillate” is uncommon English (outside the top frequency list), classed as a verb. The kind of spelling people second-guess.

Unranked
below top-frequency English
9
letters

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - To sway unsteadily from one side to the other; oscillate.

Corpus desk

Index EN-vacillate · vacillate · English

vacillate · unranked · 0 variants · 0 confusables

  • FREQ-UNRANKED Unranked
  • LEN-LONG 9 letters
  • VOW-4 4 vowels
  • CONFUS-0 No pairs
  • VAR-0 0 variants
  • BOOK-THIN "V" thin
  • PHOTO-UNK Peer pending

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Key facts for vacillate
PropertyValue
Headwordvacillate
LanguageEnglish
Part of speechVerb
IPA/ˈvæ.sə.leɪt/
Letters9
Misspellings tracked0
Confusable pairs0
SourceWiktionary (kaikki.org)

Long-tail rank of “vacillate” in English

vacillatefalls outside the top-100,000 ranked English words, the long-tail zone of technical, archaic, or low-frequency vocabulary, exactly where readers second-guess spellings most.

Beyond rank #100,000. Source: FrequencyWords open word-frequency list.

Rare enough to double-check

vacillate is uncommon English outside the top frequency list, classed as averb, transcribed /ˈvæ.sə.leɪt/. Rarity is why readers land here mid-draft. 2 senses are on record.

vacillate doesn't appear in our generated misspelling index, a sign its spelling follows regular English conventions. Our confusable-pair dataset has no match for it, since no other headword is close enough in sound or shape to pair with it.

Etymologically, the entry records: From Latin vacillātum, supine form of vacillō (“sway, waver”). The correct English form is vacillate, spelled V-A-C-I-L-L-A-T-E.

Definition

  1. 1
    To sway unsteadily from one side to the other; oscillate.
  2. 2
    To swing indecisively from one course of action or opinion to another.

Recorded use

Wiktionary examples

These source excerpts show how vacillate appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. Its [the barometer's] normal register in the Paumotus [the Tuamotus] was 29.90, and it was quite customary to see it vacillate between 29.85 and 30.00, or even 30.05; […]
  2. Courageous, patriotic, yet vacillating, many of the noblest principles and the purest intentions, men of large possessions and ancient names, under the afflicting circumstances of the times, failed to render service to their unhappy country, but involved themselves in irremediable ruin.

Etymology

From Latin vacillātum, supine form of vacillō (“sway, waver”).

Synonyms

This word in other languages

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "vacillate"?
"vacillate" is spelled V-A-C-I-L-L-A-T-E. The IPA pronunciation is /ˈvæ.sə.leɪt/.
What does "vacillate" mean?
As a verb, "vacillate" means: To sway unsteadily from one side to the other; oscillate.
How do you pronounce "vacillate"?
The IPA (International Phonetic Alphabet) transcription for "vacillate" is /ˈvæ.sə.leɪt/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "vacillate"?
From Latin vacillātum, supine form of vacillō (“sway, waver”). See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list