An AI hallucination is when an AI says something that is wrong, and it is confident about it. It does not know it is wrong. A right answer and a wrong answer come out looking exactly the same. Same tone. Same certainty. No warning. That is what makes it a hallucination and not just an error. An error you can catch. A hallucination looks like the truth. The problem is not that the AI is wrong. The problem is that you cannot tell.