Cut-off is the action of stopping a process abruptly, such as shutting off the flow of propellant to a rocket engine. (MECO) Main engine cut off occurs at stage separation (where the booster engines cut off and the booster disconnects from the space capsule.

At Space X the booster returns to Earth and is landed on a drone ship. This saves approximately 36 million dollars each launch.

Watch this video demonstrating the engine cut-off in transit SpaceX Starlink launch on October 27 2022