1.To settle upon (public land) with a right of preemption, as under the laws of the United States; to take by preemption. (Also spelled pre-empt)
2.To acquire or take for oneself first (an object or right), thereby preventing others from acquiring; to appropriate; to arrogate.
3.To supplant or take the place of (an action), due to changes in circumstances or priorities; as, the regular meeting was preempted by an emergency conference.
4.To prevent or delay (an event) by acting beforehand; to head off; to preclude.
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