Foam at the mouth
Definition 1 of 3
Pro Tip 1/3Extreme Anger
Use to emphasize a very strong, sometimes exaggerated, anger in informal situations. 
He was foaming at the mouth when he saw the scratch on his car.
Pro Tip 2/3Informal Speech
Common in spoken English and informal texts like emails or messages to friends. 
My mom started foaming at the mouth when she heard I was suspended.
Pro Tip 3/3Figurative Use
It's not literal foam; it's a metaphor for the extent of one's anger. 
The coach began foaming at the mouth after the referee's call.