A word that's wrong.

If you defeat someone, it means that you are the winner. But if something was a defeat for you, like if you say, "In my life there have been many defeats," it means losses, instead of wins, and that is wrong.

The person who designed this word was trying to keep English-speaking people on their toes, the way that your literature teacher puts the question "What did David Copperfield do for a living" on the test just to trick anyone who did not read the book into answering magician.