flare-up flare-up {n.} The reoccurrence of an infection or an armed conflict. He had a flare-up of his arthritis. There was a bad flare-up of hostilities in some countries. Categories: add yours {n.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: F Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Comment on this entry