Noun
A chamber or cavity filled with air, in an animal or plant.
A cavity containing air to act as a spring for equalizing the flow of a liquid in a pump or other hydraulic machine.
Source: Webster's dictionaryBeneath the bowl is an air chamber which serves to cool, dry, and mellow the smoke. Source: Internet
Reeds fixed on the inner side of the reed plate (within the comb's air chamber) respond to blowing, while those fixed on the outer side respond to suction. Source: Internet