Inflexible /(?)/

In·flex·i·ble

Inflexible

a.
  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.”
    — Miltom.
    A man of upright and inflexible temper . . . can overcome all private fear.
  3. Incapable of change; unalterable; immutable.
    The nature of things is inflexible.