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}.

Source : WordNet®

vacillate
     v 1: be undecided about something; waver between conflicting
          positions or courses of action; "He oscillates between
          accepting the new position and retirement" [syn: {hover},
           {vibrate}, {oscillate}]
     2: move or sway in a rising and falling or wavelike pattern;
        "the line on the monitor vacillated" [syn: {fluctuate}, {waver}]