POST. 1. Short for power-on self-test, the POST is a test the computer must complete to verify all hardware is working properly before starting the remainder of the boot process.If the computer passes the POST the computer may return a single beep and if unsuccessful generate a beep code to indicate the error and not boot.hort for power-on self-test, the POST is a test the computer must complete to verify all hardware is working properly before starting the remainder of the boot process.