1. (verb)outburst, burst, flare-up a sudden intense happening "an outburst of heavy rain"; "a burst of lightning"
2. (verb)flare up ignite quickly and suddenly, especially after having died down "the fire flared up and died down once again"
3. (verb)erupt, irrupt, flare up, flare, break open, burst out erupt or intensify suddenly "Unrest erupted in the country"; "Tempers flared at the meeting"; "The crowd irrupted into a burst of patriotism"
Definition of flare up 
