C16: from Latin vacillāre to sway, of obscure origin
vacillate for learners of English
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Word forms: vacillates, vacillating, vacillated
If you vacillatebetween two alternatives or choices, you keep changing your mind. [formal] [V + between] ⇒ She vacillates between men twice her age and men younger than she. [+ on, V] ⇒ We cannot vacillate on the question of the party's leadership.
vacillation (væsɪleɪʃən)Word forms: vacillationsvariable noun ⇒ He accused President Carter of vacillation and retreat. ⇒ ...Stalin's miscalculations and vacillations.