A crime that you are guilty of because you are THINKING of doing something bad. (i.e. In 1984's Oceania, spending time alone is almost a crime because it's considered odd, and odd people are a threat to a stable environment such as theirs.)
also, see patriot act. (i.e. when you check anarchist cookbook out from the library or something, the gov might have the right to go into your home and tap your phone and computer. And it's all perfectly legal since you might be a terrorist.)
This idea is prevalent in the dystopian novel "1984," by british author George Orwell.