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One of several small auxiliary gasbags placed inside a balloon or a nonrigid airship that can be inflated or deflated during flight to control and maintain shape and buoyancy.
[French ballonnet, diminutive of ballon, balloon; see balloon.]
(Aeronautics) an air or gas compartment in a balloon or nonrigid airship, used to control buoyancy and shape
[C20: from French ballonnet a little balloon]
an air or gasbag compartment in a balloon or airship used to control buoyancy and shape.
[1900–05; < French]