WordWeb Online

1. An unrestrained expression of emotion
   - effusion, gush, blowup [informal], ebullition, blow-up [informal]
    
2. A sudden intense happening
   "an outburst of heavy rain";
   - burst, flare-up
    
3. A sudden violent disturbance
   - tumultuous disturbance

Derived forms: outbursts

Type of: disturbance, expression, happening, manifestation, natural event, occurrence, occurrent, reflection, reflexion [Brit]

Encyclopedia: Outburst