what does it mean to preempt something

To preempt something means to take action in advance to prevent something from happening or to do or say something before someone else does, thereby making their action or words unnecessary or ineffective. It can also mean to replace or take the place of something considered more important or urgent, such as a TV program being preempted by a special broadcast. The term comes from Latin roots meaning "to buy before" and implies seizing or acting before others to gain priority or control.