noun, na-adjective
stubbornly honest; rigidly upright
Describes a person who is so honest and principled that they are inflexible or uncompromising. Often carries a nuance of being too straight-laced.
彼は正直一徹な性格で、嘘をつくことができない。
He has a stubbornly honest personality and cannot tell a lie.
正直一徹な人ほど、時に周囲と衝突しやすい。
The more rigidly honest a person is, the more likely they are to clash with others at times.
Compound of 正直 (honest) and 一徹 (stubborn, obstinate). The exact historical derivation is uncertain, but the combination yields the meaning of being uncompromisingly honest.