Merriam-Webster Collegiate Dictionary - preempt

 verb  Etymology: back-formation from ~ion  Date: 1850  transitive verb  1. to acquire (as land) by ~ion  2. to seize upon to the exclusion of others ; take for oneself the movement was then ~ed by a lunatic fringe  3. to replace with something considered to be of greater value or priority ; take precedence over the program did not appear, having been ~ed by a baseball game — Robert MacNeil  4. to gain a commanding or preeminent place in  5. to prevent from happening or taking place ; forestall, preclude  intransitive verb to make a ~ive bid in bridge  • ~or noun