Criminal List in UnderWorld , When you think of a criminal, the first thing that may come to mind is a person as terrible as a murderer. But the word is much broader. A person who violates the law is technically a criminal, even if the crime does not pay a speeding fine. You can also talk about criminal activity, that is, illegal things. Many television shows are about police officers and lawyers trying to catch criminals involved in all sorts of exciting criminal activities.