rigid

Etymology

From Middle English rigide, from Latin rigidus (“stiff”), from rigeō (“I am stiff”). Compare rigor. Merged with Middle English rigged, rygged, rugged (“upright like a spine, rigid”, literally “ridged”), from ridge + -ed.

adj

1. Stiff, rather than flexible.
2. Fixed, rather than moving.
   A sunflower, four more, one bowed, and horses in the distance standing rigid and still as toys. 2011, David Foster Wallace, The Pale King, Penguin Books, page 5
3. Rigorous and unbending.
4. Uncompromising.

noun

1. (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.
   The rigid could reach the greatest sizes and speeds of any airship, but was expensive to build and bulky to store. Rigids fell out of favor after the R101 and Hindenburg disasters made the type seem unsafe to the travelling public.
2. A bicycle with no suspension system.