The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

            His vacillations, always exhibited most pitiably in
            emergencies.                          --Macaulay.
      [1913 Webster]

   2. Unsteadiness of purpose; changeableness.
      [1913 Webster]

            There is a vacillation, or an alternation of
            knowledge and doubt.                  --Jer. Taylor.
      [1913 Webster]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "vacillation":
   alternation, capriciousness, chance, chanciness, changeableness,
   dallying, demurral, dillydallying, equivocation, erraticism,
   erraticness, fickleness, fluctuation, frequency, frequency band,
   frequency spectrum, harmonic motion, hesitancy, hesitation,
   incalculability, incertitude, indecision, indecisiveness,
   indemonstrability, indeterminacy, indetermination, indeterminism,
   irresolution, libration, luck, nutation, oscillation, pendulation,
   periodicity, randomness, resonance, resonance frequency, seesawing,
   shifting, shilly-shally, shilly-shallying, shuffling, suspense,
   suspensefulness, teeter-tottering, teetering, tottering,
   unaccountability, uncertainness, uncertainty,
   uncertainty principle, undecidedness, undeterminedness,
   unforeseeableness, unpredictability, unprovability, unsureness,
   unverifiability, variation, vibrancy, vibratility, vibration,
   vicissitude, wavering, whimsicality, wobbling