Hidebound describes someone so stubbornly attached to old ways of thinking that they refuse to consider new ideas, even when change would help.

A hidebound teacher might insist that students only learn math one particular way, even when some students would understand better with a different approach. A hidebound coach might refuse to try new training methods that could help the team improve. When a company becomes hidebound, it keeps using outdated systems simply because “we've always done it that way,” even as competitors race ahead with better solutions.

Notice that hidebound is harsher than simply being traditional or cautious. A person can value tradition while still being open to improvement. But someone hidebound has let their attachment to the familiar become a prison. Their thinking has lost its flexibility.