Boil Over Meaning

(idiomatic, of anger, etc.) To reach the point where aggressive action is taken.

Example:   I forgot about the rice and it boiled over.‎
1913, Joseph C. Lincoln, chapter 13, Mr. Pratt's Patients:
  He b'iled right over, and the tongue-lashing he give that boss Right Liver beat anything I ever listened to. There was heap of Scriptur' language in it, and more brimstone than you'd find in a match factory.
2013, Phil McNulty, Liverpool 1-0 Man Utd, BBC Sport, 1 September 2013:
  But as the half progressed, Liverpool's pressure and high-tempo passing game increased United's frustration and it threatened to boil over on the stroke of half-time when Van Persie, who had already been booked, was involved in angry verbal exchanges with several Liverpool players, particularly Gerrard.