A person who is headstrong but to the point where theyre foolishly or irrationally stubborn
; obstinately opinionated, especially in refusing to consider alternatives.
Basically theyre hard to work with because he/she believes they have all the answers, regardless of the facts or opinions.
Will is very bullheaded. He literally shuns my ideas because he thinks he has all the answers.
You are the most bullheaded person I've ever known!