Fig. Either improve one's performance (or behavior) or leave. (Used as a command.) Okay, Tom. That's the end. Shape up or ship out! John was late again, so I told him to shape up or ship out.
something that you say in order to tell someone that if their behaviour does not improve, they will have to leave This is the third serious mistake you've made this month. It's not good enough - you're going to have to shape up or ship out.