Preemptive bidding is getting to your contract fast (in few bids) when you think the opponents can make a higher contract. You hope that the lack of bidding room will make finding the best contract very difficult for the opponents.

Preempt (also spelled "Pre-empt") is a bid in contract bridge whose primary function is to take up bidding space from the opponents. A preemptive bid is usually made by jumping, i.e. skipping one or more bidding levels. Since it deprives the opponents of the bidding space, it is expected that they will either find a wrong contract (too high or in a wrong denomination) of their own, or fail to find any.

To settle upon (public land) with a right of preemption, as under the laws of the United States; to take by preëmption.

acquire by preemption

To act in advance.