also: わからずや
noun
Refers to a stubborn, unreasonable person who won't listen to reason. The kanji form 没分暁漢 is a rare yojijukugo; in modern Japanese, わからずや is the usual written form.
彼はまったくのわからずやで、誰の言うことも聞かない。
He's a complete blockhead and won't listen to anyone.
あのわからずやを説得するのは無理だ。
It's impossible to persuade that obstinate person.