incapable of being physically moved; fixed
steadfast in purpose or intention; unalterable, unyielding
not capable of being affected or moved in feeling; impassive
not liable to be removed; permanent in place or tenure; fixed
that which can not be moved; something which is immovable
Fixed, rather than moving.
Stiff, rather than flexible.
Uncompromising.
Rigorous and unbending.
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.