From Longman Dictionary of Contemporary Englishair lockˈair lock noun [countable] 1 TTWTTSa small room used for moving between two places that do not have the same air pressure, for example in a spacecraft2 TAIRa small amount of air in a pipe that stops liquid flowing through it
Examples from the Corpus
air lock• Finally, they were let through an air lock guarded by massive metal doors into the reactor structure.• Gripping a hand rail, she waited for the door of the air lock to open.• Through the air lock she went, down the metal steps, and out on to the Moon's dusty surface. 