Definition of "airlock"

airlock

noun
plural airlocks
1. 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.
  Quotations
  At the head of the machine, we are shown the airlock through which people have to pass to work on the cutting head, as it operates under pressure to prevent leakages into the tunnel.
  2022 March 23, Paul Bigland, “HS2 is just 'passing through'”, in RAIL, number 953, page 42
2. (architecture, informal) 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.
3. Alternative form of air lock