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1. Ignite quickly and suddenly, especially after having died down
   "the fire flared up and died down once again"
    
2. Erupt or intensify suddenly
   "Unrest flared up in the country";
   - erupt, irrupt, flare, break open, burst out

1. A sudden intense happening
   - outburst, burst

Derived forms: flares up, flaring up, flared up, flare-ups

Type of: deepen, happening, ignite, intensify, light, natural event, occurrence, occurrent

Encyclopedia: Flare-up