D defs.my
Entry 1 sense Webster, 1913

Retroactive

/rĕtˌ-rō-ăk'-tĭv/ · Re·tro·act·ive · IPA /ˌɹɛ.tɹoʊˈæk.tɪv/
01 a. Fitted or designed to retroact; operating by returned action; affecting what is past; retrospective.
  1. 1.
    Fitted or designed to retroact; operating by returned action; affecting what is past; retrospective.
Phrases & compounds
Retroactive 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.