aerostat

n. device that floats in the air (i.e. air ballon, blimp, dirigible); balloonist, pilot of a lighter-than-air aircraft

An aerostat is a lighter than air craft including free balloons, airships, and moored balloons. Such a vehicle is lifted by buoyancy, containing a gas less dense than air within an envelope.The term "aerostat" comes from the fact that buoyancy is technically said to provide "aerostatic" lift in that the force upwards arises without movement through the surrounding air mass. This contrasts with aerodynamic  lift which requires the movement of at least some part of the aircraft through the surrounding air mass.
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n. aerostat, device that floats in the air (i.e. ballon, blimp, dirigible)

n. aerostat

(n.)
A balloonist; an aeronaut.
  

(n.)
A balloon.