Definition of "rigid"

Stiff, rather than flexible.  examples

Fixed, rather than moving.  quotations  examples

Rigorous and unbending.  examples

Uncompromising.  examples

(aviation) An airship whose shape is maintained solely by an internal and/or external rigid structural framework, without using internal gas pressure to stiffen the vehicle (the lifting gas is at atmospheric pressure); typically also equipped with multiple redundant gasbags, unlike other types of airship.  examples

A bicycle with no suspension system.  examples