boil over

[boil over] {v. phr.} 1. To rise due to boiling and overflow down the sides of a pan or a pot.

"Watch out!" Jane cried. "The milk is boiling over on the stove!"

2. To become enraged to the point of being unable to contain oneself.

John took a lot of abuse from his boss, but after 25 minutes he suddenly boiled over and told him what he thought of him.