IPA: /ˌrɛtrəʊˈækʃən/
KK: /rɛtroʊˈækʃən/
A noun that refers to an action that affects a previous time or an action that is a response to another action.
The retroaction of the new law meant that it would apply to events that occurred last year.
Retroaction → It is formed from "retro-" (meaning backward) and "actio" (from Latin, meaning action). The word describes an action that has effects or influences that go backward in time or refer to past actions.
Think of 'backward' ('retro-') actions ('actio') that influence the present — that's what retroaction means.