‘Alan Smithee’ is a common pseudonym for directors whose film was clearly taken away from her/him and recut heavily against her/his wishes in ways that completely altered the film.
The Directors Guild contract generally does not permit a director to remove her/his name from films. The Directors Guild has been striving for decades to establish the director as the “author” of a film, and part of getting the credit for the successes is taking the blame for the failures. The only exceptions they make are cases in which a film was clearly taken away from a director and recut heavily against her/his wishes in ways that completely altered the film. Directors are required to appeal to the Guild in such cases. If the appeal is successful, their name is replaced by Alan Smithee. So if you notice a film directed by Alan Smithee, it is certain it is not what its director intended, and likely that it is not any good.