It is when you expand the powers of something illegally against the constitution.
read this for examples:
http://freedomsite.net/articles.htm
It was the british that wanted the goverment money so of that they wanted to get it and they will die
The Supreme Court of the Unites States may declare laws unconstitutional. It is the only branch legally able to do that.
The law is nullified and may not be enforced against anyone, but it is not "repealed" in the sense that a legislature repeals laws it has made earlier. The unconstitutional law will remain on the books until the appropriate legislature makes an actual repeal to clear the books of the now useless law.