A Ghost Page is a Page automatically excluded from all the sitemaps and hyper-lists, not cached by the WP Super Cache plugin and yet, a Page for which The Permalinks Cascade disallows the crawling without showing up its path into the
robots.txt file generated by WordPress. Generally a Ghost Page has few to no inbound links. An example of Ghost Page would be the landing page of a successful PayPal transaction, namely an order confirmation page.
To prevent the indexing of a Ghost Page without resorting to a
Disallow rule that might be used by bad-disposed robots to uncover the Page, The Permalinks Cascade sends back an
X-Robots-Tag HTTP Header that a trustworthy crawler should take into account. This is also one of the reasons why the plugin hinders the "supercaching" of such a Page.
Flagging a Page as Ghost Page
This can be done by just ticking the 'This is a Ghost Page' checkbox in the editor screen of the Page you want it to be cloaked, and then clicking on the 'Update' button:
To flag multiple Pages at once, the 'Bulk Edit' functionality available in the 'Pages' screen of WordPress is your friend.
Note that neither Posts nor Custom Posts can be flagged as Ghost Pages.