Source : Webster's Revised Unabridged Dictionary (1913)

Vacillate \Vac"il*late\, v. t. [imp. & p. p. {Vacillated}; p.
   pr. & vb. n. {Vacillating}.] [L. vacillare, vacillatum; cf.
   Skr. va[~n]c.]
   1. To move one way and the other; to reel or stagger; to
      waver.

            [A spheroid] is always liable to shift and
            vacillatefrom one axis to another.    --Paley.

   2. To fluctuate in mind or opinion; to be unsteady or
      inconstant; to waver.

   Syn: See {Fluctuate}.

Vacillating \Vac"il*la`ting\, a.
   Inclined to fluctuate; wavering. --Tennyson. --
   {Vac"il*la`ting*ly}, adv.

Source : WordNet®

vacillating
     adj : uncertain in purpose or action [syn: {vacillant}, {wavering}]