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1. Uncertain in purpose or action
   "If the cat was in the vacillating phase, there was increased tension, restlessness, a startle reaction"
   - vacillant, wavering

1. Be undecided about something; waver between conflicting positions or courses of action
   "He vacillates between accepting the new position and retirement"
   - hover, vibrate, oscillate, blow hot and cold
    
2. Move or sway in a rising and falling or wavelike pattern
   "the line on the monitor vacillated"
   - fluctuate, waver

See also: irresolute, vacillation, vacillator

Type of: balk, baulk [Brit], hesitate, swing, waffle, waver