gatehouse

noun4

1. •
   A lodge besides the entrance to an estate; often the residence of a gatekeeper; also a dwelling formerly used as such a residence.
2. •
   A shelter for a gatekeeper.
3. •
   (historical) A fortified room over the entrance to a castle or over the gate in a city wall
4. •
   An airport terminal structure or section containing a boarding gate; a departure lounge.