bullheaded
Very stubborn and unwilling to listen or change your mind.
Bullheaded means stubbornly refusing to change your mind or consider other viewpoints, even when you're clearly wrong or when better information comes along. Picture a bull lowering its head and charging forward no matter what stands in its way. That's the image behind this word.
A bullheaded person digs in their heels and won't budge. If your friend insists the fastest route home goes through the park even after you show them a map proving otherwise, they're being bullheaded. If a student refuses to try a teacher's helpful suggestion because they're convinced their own method is better (despite failing repeatedly), that's bullheaded behavior.
Being bullheaded is different from being confident or standing up for what's right. Confidence means trusting yourself while staying open to learning. Bullheadedness means closing yourself off from any possibility that you might be mistaken. A confident person can say “I was wrong” when they discover new information. A bullheaded person would rather fail than admit they should reconsider.
The word carries a critical tone. Nobody admires bullheadedness because it leads to avoidable mistakes and frustration. When people call someone bullheaded, they're usually frustrated that the person won't listen to reason. It's the opposite of being flexible, thoughtful, or open-minded.