A ninja edit is an change made to a published post or article (typically on a bulletin board) that preempts the first response made. Often, the existence of the ninja edit is only made clear by a reference to the mistake or inconsistency in the original article by the response. In such a case, the author of the response began writing before the ninja edit, but submitted the response after the ninja edit had been made.

http://www.urbandictionary.com/defin...m=ninja%20edit