A vestibule, foyer or entranceway with doors to the exterior on one end and doors to the interior on the other, functioning to keep indoor and outdoor air, humidity, and air temperatures separate.
A sealed, airtight chamber, such as in a manned spacecraft or submarine, used to provide access to and from the sealed area without allowing air out or water in.
The passage of a door; a door-shaped entrance into a house or a room.