pre·emp·tive /-ˈɛm(p)tɪv/
  先買的,先買權的,有先買權的
  preemptive
  佔先資源
  Pre·ëmp·tive a. Of or pertaining to preëmption; having power to preëmpt; preëmpting.
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  preemptive
       adj : designed or having the power to deter or prevent an
             anticipated situation or occurrence; "a preemptive
             business offer"