To delete a page, make the first word of the page: DeletedPage. You can write anything else you want on the page; you should write at least a word or five explaining why (even if it's obvious to you). A useful idiom looks something like
DeletedPage: off-topic Original text goes here; e.g. Natalie Portman is well known for her role in The Professional.
Pages tagged with DeletedPage are deleted after two weeks (actually, the expiry timeout of the KeptPages?) of no edit activity. In practice, this usually means after someone important remembers to do maintenance.
Pages that are deleted are permanently lost. They are not restorable from any backups you may have heard exist, no matter how reputable the source of that rumour was. Therefore, it is up to the community to ensure that pages aren't deleted recklessly.
From DeletedPage and PageDeletion