A gatekeeper is a person who controls access to something, for example via a city gate. In the late 20th century the term came into metaphorical use, referring to individuals who decide whether a given message will be distributed by a mass medium.
英英词典
gate keeper n.
someone who controls access to something
synonymous: gatekeeper
someone who guards an entrance
synonymous: doorkeeper, doorman, door guard, hall porter, porter, gatekeeper, ostiary