'flare up' definitions:

Definition of 'flare up'

(from WordNet)
verb
Ignite quickly and suddenly, especially after having died down; "the fire flared up and died down once again"
verb
Erupt or intensify suddenly; "Unrest erupted in the country"; "Tempers flared at the meeting"; "The crowd irrupted into a burst of patriotism" [syn: erupt, irrupt, flare up, flare, break open, burst out]

Synonyms of 'flare up'

From: Moby Thesaurus