Fly the coop
Definition 1 of 1
Pro Tip 1/3Escape Metaphor
Imagine a chicken escaping from a coop; it signifies gaining freedom or leaving restrictions. 
Tired of the strict rules at home, she decided to fly the coop when she turned 18.
Pro Tip 2/3Sneaky Departure
It implies leaving quietly without informing others, often to avoid confrontation. 
He didn't want to cause a scene, so he chose to fly the coop early in the morning.
Pro Tip 3/3Emphasize Frustration
It's often used when someone leaves a place out of frustration or dissatisfaction. 
The employees threatened to fly the coop if conditions didn't improve.