verb (used without object), vac·il·lat·ed, vac·il·lat·ing.

to waver in mind or opinion; be indecisive or irresolute: His tendency to vacillate makes him a poor leader.
to sway unsteadily; waver; totter; stagger.
to oscillate or fluctuate.

Origin of vacillate

1590–1600; < Latin vacillātus (past participle of vacillāre to sway to and fro); see -ate1
Related formsvac·il·la·tor, noun

Synonyms for vacillate

1. hesitate. See waver1. 2. reel. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for vacillate

Contemporary Examples of vacillate

Historical Examples of vacillate

  • He may pause, but he must not hesitate,—and tremble, but must not vacillate.

  • Long did he vacillate whether Tom Keane should not be arrested on suspicion.

    Roland Cashel

    Charles James Lever

  • They vacillate, conforming now to the interest of the wage-workers, now to the interest of the employers.


    John Spargo

  • Why do you vacillate, and keep us all in the dark as to what you mean?

  • As if it were possible to wait now, to weigh, vacillate, hesitate!

    The Death of the Gods

    Dmitri Mrejkowski

British Dictionary definitions for vacillate


verb (intr)

to fluctuate in one's opinions; be indecisive
to sway from side to side physically; totter or waver
Derived Formsvacillation, nounvacillator, noun

Word Origin for vacillate

C16: from Latin vacillāre to sway, of obscure origin
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for vacillate

1590s, "to sway unsteadily," from Latin vacillatum, from vacillare (see vacillation). Meaning "to waver between two opinions or courses" is recorded from 1620s. Related: Vacillated; vacillates; vacillating.

Online Etymology Dictionary, © 2010 Douglas Harper