Nouns

(n)preemption, pre-emptionthe judicial principle asserting the supremacy of federal over state legislation on the same subject
(n)preemption, pre-emptionthe right of a government to seize or appropriate something (as property)
(n)preemption, pre-emptionthe right to purchase something in advance of others
(n)preemption, pre-emptiona prior appropriation of something“the preemption of bandwidth by commercial interests”