(Namespace: plural glossary)

“Gatekeeper” is one word with three completely unrelated plural-relevant definitions.

In non-system-hopping systems, a gatekeeper is a headmate who controls some of a system's internal functions. They may, for instance, control fronting and switching, or who can be coconscious with whom, or the permissible contents of internal communication and memory sharing, etc.

A gatekeeper may be, but is not necessarily, an internal self-helper.

In system-hopping systems, a gatekeeper is a headmate who controls a system's access to the headspaces of other systems.

In syscourse, a gatekeeper is a system exclusionist.