nonrigid

Adjective

 * 1) Not rigid; flexible.
 * 2)  That maintains its shape only by internal gas pressure.

Noun



 * 1)  An airship that maintains its shape only by internal gas pressure.

Usage notes

 * dirigible is not a synonym, but a hypernym; it refers to all steerable self-propelled airships, whether rigid, semirigid, or nonrigid.