ret·ro·ac·tive /-ˈæktɪv/
  (a.)反動的,追溯的,有追溯力的
  Re·tro·act·ive a.  Fitted or designed to retroact; operating by returned action; affecting what is past; retrospective.
  Retroactive law or Retroactive statute Law, one which operates to make criminal or punishable, or in any way expressly to affect, acts done prior to the passing of the law.
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  retroactive
       adj 1: descriptive of any event or stimulus or process that has an
              effect on the effects of events or stimuli or process
              that occurred previously [ant: proactive]
       2: affecting things past; "retroactive tax increase"; "an
          ex-post-facto law"; "retro pay" [syn: ex post facto, retro]