Preemptive

[prɪ'emptɪv] or [,primptɪv]

(adj.) designed or having the power to deter or prevent an anticipated situation or occurrence; 'a preemptive business offer' .

Checker: Trent--From WordNet

(a.) Of or pertaining to preemption; having power to preempt; preempting.

Editor: Sallust