What is the meaning of Rigid?

Stiff, rather than flexible.

Having inflexible thoughts, opinions, or beliefs.

Fixed, rather than moving.

Rigorous and unbending.

Uncompromising.

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.

A bicycle with no suspension system.

to stretch, to distend

to rule, direct

rigid

Source: wiktionary.org