QED

- abbreviation for quod erat demonstrandum (= Latin for 'which was to have been proven'). Written after an argument in mathematics to show that you have proven something that you wanted to prove.(informal) QED is also used to show that something you have just said or done is the solution to a problem or the answer to a question.Well, if you want to get into the final, all you have to do is beat everyone in all the heats. QED.