From Longman Dictionary of Contemporary Englishboil up phrasal verb1 SERIOUS SITUATIONif a situation or emotion boils up, bad feelings grow until they reach a dangerous level She could sense that trouble was boiling up at work. He could feel the anger boiling up inside him.2 DFC boil something ↔ up to heat food or a liquid until it begins to boil Boil the fruit up with sugar. → boil→ See Verb table