Airlock and Obstacle

Airlock noun - A chamber that provides access to space where air is under pressure.

Obstacle and airlock are semantically related. In some cases you can use "Obstacle" instead a noun "Airlock".

Obstacle noun - Something that makes movement or progress difficult.

Airlock and obstacle are semantically related. Sometimes you can replace term "Airlock" with "Obstacle", this nouns are similar.