1. action that works backward or has an effect on something that happened earlier
Usage: formal; technical
2. the application of a law or rule to events that occurred before the law was enacted
Usage: legal

Examples

• The new tax law’s retroaction affected transactions from the previous year.
• Scientists studied the retroaction of the chemical process on earlier reactions.
• The court ruled against the retroaction of the statute to past cases.
• The policy’s retroaction created confusion among businesses.
• Legal experts debated the constitutional limits of retroaction.
• The retroaction of the regulation surprised many industry professionals.