The Collaborative International Dictionary of English v.0.48:
Flare-up \Flare"-up`\, n. 1. A sudden burst of anger or passion; an angry dispute. [Colloq.] [1913 Webster] 2. A sudden bursting into flame; a flaring. [Webster 1913 Suppl.]WordNet (r) 3.0 (2006):
flare-up n 1: a sudden intense happening; "an outburst of heavy rain"; "a burst of lightning" [syn: outburst, burst, flare-up]