Here's a breakdown:
* Shape up: This refers to improving your work, attitude, or behavior to meet expectations.
* Ship out: This means to leave, often referring to being fired or dismissed.
Essentially, the idiom is a warning or ultimatum. It tells someone that they need to change their ways or face consequences, usually losing their job or position.
Example:
"The boss gave everyone a warning: 'Shape up or ship out. We're not tolerating any more missed deadlines.'"