"User created XXX" is not a formal (or informal) concept in
Java, so I think it would be hard to give you a definition. It's just a couple of English words, which presumably mean "a class (or method) written by the user."
Maybe if you gave us some context -- i.e., where you came across this term and why you need it to be clarified -- we could help more. But as it is, it's tautological at best.