Inflexible

Webster's Dictionary of the English Language

·adj Incapable of change; unalterable; immutable.

II. Inflexible ·adj Not capable of being bent; stiff; rigid; firm; unyielding.

III. Inflexible ·adj Firm in will or purpose; not to be turned, changed, or altered; resolute; determined; unyieding; inexorable; stubborn.