To temper a piece of meat means to control the temperature of it at all stages of cooking.
Tempering meat is a very important part of the cooking process in order to get consistent results every time and should not be overlooked, particularly with beef.
There are a lot of considerations when cooking any type of meat so if you take the time to temper it, it will mean better, more consistent results. Using a meat thermometer is an important tool to ensure success.