Inflexible
Inflexible , adjective
[Latin inflexiblis: compare French inflexible. See In- not, and Flexible.]
1.
Not capable of being bent; stiff; rigid; firm; unyielding.
2.
Firm in will or purpose; not to be turned, changed, or altered; resolute; determined; unyieding; inexorable; stubborn.
“Inflexibleas steel.”
A man of upright and inflexible temper... can overcome all private fear.
3.
Incapable of change; unalterable; immutable.
The nature of things is inflexible.