Stubborn means unwilling to change one's mind or behaviour, even when faced with strong opposition or reason. It often implies a strong-willed and inflexible attitude.
Here are some synonyms for stubborn:
* Headstrong
* Obstinate
* Pigheaded
* Intransigent
* Unyielding
* Tenacious (can have a positive connotation depending on the context)
Example:
"Despite the evidence presented, the witness remained stubborn in his denial."