boil up phrasal verb ( see also ↑ boil )
1 . if 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 . boil something ↔ up to heat food or a liquid until it begins to boil:
Boil the fruit up with sugar.