Definition of "flare up"

flare up

verb
third-person singular simple present flares up, present participle flaring up, simple past and past participle flared up
1. (intransitive) To burn brightly again.
2. (intransitive) To become more intense suddenly.
3. (intransitive, sometimes with “out” instead of “up”) To burst out suddenly, as in anger.
  Quotations
  “Well,” I says, “I cal'late a body could get used to Tophet if he stayed there long enough.” ¶ She flared up; the least mite of a slam at Doctor Wool was enough to set her going.
  1913, Joseph C. Lincoln, chapter 5, in Mr. Pratt's Patients
  "It's my Welsh half that comes out when I flare up. Let the conjurors take their dirty money and let the rich folk keep their purses shut."
  1925 July – 1926 May, A[rthur] Conan Doyle, “(please specify the chapter number)”, in The Land of Mist (eBook no. 0601351h.html), Australia: Project Gutenberg Australia, published April 2019