Userei il sinonimo essendo un dirigibile floscio, per intederci, quello usato per le pubblicità, quindi è più un pallone che un dirigibile

There is some confusion around the term aerostat with regard to airships. This confusion arises because aerostat has two different meanings. One meaning of aerostat refers to all craft that remain aloft using buoyancy (static not dynamic lift): in this sense airships are a type of aerostat. The narrower and more technical meaning of aerostat refers only to tethered or moored balloons: in this sense airships are not aerostats.


A blimp, or non-rigid airship, is a floating airship without an internal supporting framework or keel. A non-rigid airship differs from a semi-rigid airship and a rigid airship (e.g., a Zeppelin) in that it does not have any rigid structure, neither a complete framework nor a partial keel, to help the airbag maintain its shape. Rather, these aircraft rely on both a higher pressure of the lifting gas (usually helium) inside the envelope and the strength of the envelope itself.

The term "blimp" refers only to free-flying aircraft. The term is sometimes erroneously used to refer to the tethered craft known as moored balloons. While often very similar in shape, moored balloons have no propulsion and are tethered to the ground.

http://en.wikipedia.org/wiki/Blimp