However, there are words that are commonly used with similar meanings to "illegal", often including prefixes:
* Illicit: This is the closest direct synonym for "illegal" and means "forbidden by law".
* Unlawful: This means "not permitted by law".
* Contraband: This refers to goods that are prohibited by law.
* Outlawed: This means "declared illegal".
* Forbidden: This is a broader term meaning "not allowed" but can be used in a legal context.
It's important to note that the context will determine which word is most appropriate.