Bureaucrat is the technical name used on many wiki-based sites to refer to contributors who have the technical privileges to make certain very important changes to the system, and also view information that is hidden from ordinary users. Someone who controls a user account within the Citizendium bureaucrat group may change other users' privileges, rename accounts to prevent editing, and view the IP addresses of applicants, among other procedures.
On Citizendium, bureaucrat rights are shared between various people depending on their roles. The Moderator-in-Chief, who is responsible for maintaining behaviour on the site, has bureaucrat powers. So too do technical staff. Bureaucrats usually also have administrator (sysop) powers.
Bureaucrat powers are granted to trusted individuals based on a decision by the Citizendium Council. The privileges are handed out sparingly; Council members and even the Managing Editor are not given bureaucrat rights by virtue of holding office.