(adj)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
a. [ Cf. F. rétroactif. ] Fitted or designed to retroact; operating by returned action; affecting what is past; retrospective. Beddoes. [ 1913 Webster ]
Retroactive lawor 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 ]