'Retroactive' definitions:

Definition of 'retroactive'

From: WordNet
adjective
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]
adjective
Affecting things past; "retroactive tax increase"; "an ex- post-facto law"; "retro pay" [syn: ex post facto, retroactive, retro]

Definition of 'Retroactive'

From: GCIDE
  • 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]