: a small room that has two doors which can be sealed tightly so that no air enters or leaves and that is used for moving between two spaces with different air pressures in a submarine, spaceship, etc.
Full Definition of AIR LOCK
: an intermediate chamber with two airtight doors or openings to permit passage between two dissimilar spaces (as two places of unequal atmospheric pressure)
: a stoppage of flow caused by air being in a part where liquid ought to circulate
See air lock defined for English-language learners