A more thorough explanation:

Term: STRIKE DOWN
Definition: To invalidate a law or statute; to declare it void.
Example: The Supreme Court struck down a state law that prohibited same-sex marriage.
Explanation: In this example, the Supreme Court declared the state law prohibiting same-sex marriage as invalid or void. This means that the law is no longer in effect and cannot be enforced. The court's decision to strike down the law means that same-sex couples can now legally marry in that state.