Uncompromising.
Stiff, rather than flexible.
Fixed, rather than moving.
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.
Unidirectional.
Single, simple; not complex.
A monomorphemic word, one without affixes.
An analogue in a space of arbitrary dimensionality of the triangle or tetrahedron; the convex hull of n+1 linearly independent points in n-dimensional space; in other words, the triangle, tetrahedron etc., generalized to an arbitrary number of dimensions.