pre-emptive
/-tɪv; -tɪv/ adj
of or concerning pre-emption 优先购买的; 预先采取行动的
a pre-emptive right to buy 优先购买权
pre-emptive purchase 优先购买
a pre-emptive attack/strike, ie one designed to forestall a likely enemy attack 先发制人的攻击[打击]
a pre-emptive bid, ie (in bridge) one made to prevent further bidding 先发制人的叫牌（用以阻止对方叫牌）.