retroactive

from WordNet (r) 3.0 (2006)

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},
       {retroactive}, {retro}]

from The Collaborative International Dictionary of English v.0.48

Retroactive \Re`tro*act"ive\, a. [Cf. F. r['e]troactif.]
   Fitted or designed to retroact; operating by returned action;
   affecting what is past; retrospective. --Beddoes.
   [1913 Webster]

   {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.
      [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

24 Moby Thesaurus words for "retroactive":
      a priori, antiphonal, back, backward, early, ex post facto,
      into the past, reacting, reactionary, reactive, recessive, reflex,
      reflexive, refluent, regressive, respondent, responding,
      responsive, retroactionary, retrocessive, retrograde,
      retrogressive, retrospective, revulsive

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