Scream blue murder
Definition 1 of 2
Pro Tip 1/3Loud Complaint
Used to describe someone protesting very passionately or loudly. 
She screamed blue murder about the unfair treatment at work.
Pro Tip 2/3Exaggeration
The phrase often conveys that someone is overreacting or being dramatic. 
He screamed blue murder over a tiny scratch on his car.
Pro Tip 3/3Strong Emotion
Indicates that the person's reaction is driven by strong emotions. 
She was screaming blue murder when she found out her show was cancelled.