The Collaborative International Dictionary of English v.0.48:

Vacillate \Vac"il*late\ (v[a^]s"[i^]l*l[=a]t), v. i. [imp. & p.
   p. Vacillated (v[a^]s"[i^]l*l[=a]`t[e^]d); p. pr. & vb. n.
   Vacillating.] [L. vacillare, vacillatum; cf. Skr. va[~n]c.]
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   1. To move one way and the other; to reel or stagger; to
      waver.
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            [A spheroid] is always liable to shift and
            vacillatefrom one axis to another.    --Paley.
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   2. To fluctuate in mind or opinion; to be unsteady or
      inconstant; to waver.
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   Syn: See Fluctuate.
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