A more thorough explanation:

Definition: Anything that goes against a constitution, especially the United States Constitution.

Examples:

• A law that prohibits freedom of speech is unconstitutional because the First Amendment of the US Constitution protects this right.
• A government official who is not a natural-born citizen of the United States cannot become president, according to the Constitution. Therefore, if someone who is not a natural-born citizen were to become president, it would be unconstitutional.

These examples illustrate the definition of unconstitutional because they both involve actions that are prohibited by the US Constitution. The Constitution is the highest law of the land in the United States, and any law or action that goes against it is considered unconstitutional. In the first example, the law prohibiting freedom of speech violates the First Amendment, which guarantees this right. In the second example, the Constitution explicitly states that only natural-born citizens can become president, so someone who is not a natural-born citizen becoming president would be unconstitutional.