That’s tutor talk for “I don’t know the answer to this question, it’s a question I’ve never been asked before and a question that I hope I shall never be asked again. Thank heavens it’s not one that is going to appear in any exam in the future”
There is an “Investopedia” definition on the Internet that is probably going to be of more use to you than my attempts, but you really do not need to know how to define it. You’re absolutely correct in that it is necessary to know how to apply it!