Definition of "preemption"

An act or process that preempts; a preventive or forestalling action; as:

1. The purchase of something before it is offered for sale to others.  examples

2. The purchase of public land by the occupant.  examples

3. (computing) The temporary interruption of a task without its cooperation and with the intention of resuming it at a later time.  examples

4. (law) The displacement of a lower jurisdiction's laws when they conflict with those of a higher jurisdiction.  examples