pre-empt BrE AmE , pre·empt /priˈempt/ verb [transitive]
[ Date: 1800-1900 ; Origin: preemption (17-21 centuries) , from Medieval Latin praeemere 'to buy before' ]
1 . to make what someone has planned to do or say unnecessary or ineffective by saying or doing something first:
The deal pre-empted a strike by rail workers.
2 . American English to replace a television show with a special programme or report:
Regular programming was preempted by a report on the war.
—pre-emption /-ˈempʃ ə n/ noun [uncountable]