Stubborn; unwilling to change one's opinion or behavior easily; obstinate.
彼は頑固で、人の意見をあまり聞かない。
He's stubborn and doesn't listen much to others' opinions.
祖父は頑固だが、優しいところもある。
My grandfather is stubborn, but he also has a kind side.
あの子は頑固に自分のやり方を通そうとする。
That child stubbornly insists on doing things his own way.