RETRO-
Retro-. Etym: [L. retro, adv., backward, back. Cf. Re-.]
Defn: A prefix or combining form signifying backward, back; as, retroact, to act backward; retrospect, a looking back.
RETROACT
Re`tro*act", v. i. Etym: [Pref. retro- + act.]
Defn: To act backward, or in return; to act in opposition; to be retrospective.
RETROACTION
Re`tro*ac"tion, n. Etym: [Cf. F. rétroaction.]
1. Action returned, or action backward.
2. Operation on something past or preceding.
RETROACTIVE
Re`tro*act"ive, a. Etym: [Cf. F. rétroactif.]
Defn: Fitted or designed to retroact; operating by returned action; affecting what is past; retrospective. Beddoes. Retroactive law or 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.
RETROACTIVELY
Re`tro*act"ive*ly, adv.