A Squash Ball turns into a Zombie Ball when it is hit so good that it should be dead, i.e. impossible to retrieve and award the striker a point, but miraculously comes back to life by unnatural, superhuman retrieval of the other player. It is of utmost important for the initial striker to kill the ball again, otherwise it might give the retriever and creator of the zombie ball a boost that can turn the tides of a game. A zombie ball might be created in other sports as well but has not been reported yet.
If Ramy Ashour successfully hits a backhand cross-court nick, the ball is usually dead. However some players such as Nick Mathew or Gregory Gaultier successfully return these shots and transform the ball to a zombie ball for the rest of the rally.