What term describes an action by a higher court that overturns the decision of a lower court?

The correct term for an action by a higher court that overturns the decision of a lower court is "reversal." In the judicial process, when a higher court examines the case and recognizes that the lower court's ruling was incorrect, it will issue a reversal, effectively nullifying that earlier decision. This is an essential aspect of checks and balances within the legal system, ensuring that justice is served and that lower court rulings can be reviewed and corrected if necessary.

The concept of "appeal" refers to the process by which a lower court decision is brought before a higher court for review, but it does not specify the outcome of that review; therefore, it alone does not mean that a lower court’s decision has been overturned. "Judgment" refers to the actual decision made by a court, and "affirmation" specifically indicates a situation where a higher court agrees with the lower court’s decision instead of overturning it.