Source : Webster's Revised Unabridged Dictionary (1913)

Vacillation \Vac`il*la"tion\, n. [L. vacillatio: cf. F.
   vacillation.]
   1. The act of vacillating; a moving one way and the other; a
      wavering.

            His vacillations, or an alternation of knowledge and
            doubt.                                --Jer. Taylor.

Source : WordNet®

vacillation
     n 1: indecision in speech or action [syn: {hesitation}, {wavering}]
     2: changing location by moving back and forth [syn: {swing}, {swinging}]