designating a type of airship having a flexible gas container without a supporting structure and held in shape only by the pressure of the gas within.
Origin of nonrigid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
not rigid; flexible
(of the gas envelope of an airship) flexible and held in shape only by the internal gas pressure
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012