a steerable self-propelled light-than-air aircraft.
An engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings. (14CFR1)
An aircraft that rises into the air because it is lighter than air. An airship is constructed from a metal frame containing bags filled with hydrogen or helium gas. The pilot flies the craft from a gondola attached to the bottom of an airship.