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.
- to fluctuate in one’s opinions; be indecisive
- to sway from side to side physically; totter or waver
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.