gatekeeper

noun

1. A person or group who controls access to something or somebody.

   “The sources the citations are drawn from are significant, being printed books or newspapers subject to editorial processes and gatekeepers of language standards, as opposed to unedited texts such as blogs, chatroom logs or student writing.”

2. A person who guards or monitors passage through a gate.

   “[…]“Here,” he said, stepping forward and handing twopence to the gatekeeper; “let the young woman pass.””

   “At each station is a level crossing, in addition to others away from stations, and, as both the road and rail traffic are heavy, the gatekeepers (mostly signalmen) are quite busy and have acquired well-merited mention for reducing delays to road traffic to a minimum.”

3. A common orange and brown butterfly with eyespots, Pyronia tithonus, of the family Nymphalidae.
4. In dissociative identity disorder, an aspect of the personality that controls access to the various identities.
5. One who gatekeeps.
6. A provider of core platform services with specific characteristics (Regulation (EU) 2022/1925 of the European Parliament and of the Council)