The idiom "stiff-necked" means someone who is stubborn and refuses to change their opinion or behavior, even when it is clear that they are wrong. It is often used to describe people who are inflexible and rigid in their thinking, and who are unwilling to consider other points of view.
For example, if someone is always insisting on doing things their way, even when it is obvious that their way is not working, you might say that they are "stiff-necked." Similarly, if someone refuses to listen to feedback or criticism, and insists that they are always right, you might use this idiom to describe them.
Overall, "stiff-necked" is a negative term that implies a lack of openness and flexibility. It suggests that the person in question is unwilling to learn or grow, and that they are likely to encounter problems as a result of their stubbornness.
• The university's stiff-necked academic standards made it difficult for students to graduate.
• My grandfather is so stiff-necked that he never tries anything new.
• The boss is a stiff-necked person who never listens to anyone else's opinion.
• I had to deal with a stiff-necked bureaucrat who refused to help me with my problem.
• The politician's stiff-necked attitude caused him to lose the support of his party.
• The company's stiff-necked policies caused them to lose a lot of customers.