DQ means Disqualified and it's something that virtually all competitive swimmers will have to face sometimes. At the gala (usually wearing white shirts) there will be a starter, a referee, time keepers on each lane and several judges looking at starts, turns and stroke technique. If you breach one of the rules surrounding starts, turns or stroke you may be Disqualified or DQ’d. It is of course disappointing but is still part of the learning process. What you need to do is to find out why you were DQ’d and then work with your coach in training to try to make sure it doesn't happen again.