noun
stubborn person; obstinate person; pig-headed person
Describes a person who is unyielding and refuses to change their mind, often with a negative connotation.
彼は頑固者だから、一度決めたら絶対に曲げない。
He's a stubborn person, so once he decides something, he never backs down.
あの頑固者を説得するのは無理
It's impossible to persuade that obstinate person.