WordWeb Online

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 [informal]
    
2. Move or sway in a rising and falling or wavelike pattern
   "the line on the monitor vacillated";
   - fluctuate, waver

Derived forms: vacillated, vacillates, vacillating

Type of: balk, baulk [Brit], hesitate, swing, waffle [N. Amer, informal], waver