noun, na-adjective
rustic and stubborn; boorishly obstinate
Describes a person who is rough, unsophisticated, and stubbornly sticks to their coarse ways. Often used critically or self-deprecatingly.
彼は無骨一徹な職人で、新しいやり方を絶対に受け入れない。
He is a boorishly stubborn craftsman who absolutely refuses to accept new methods.
無骨一徹な態度が災いして、彼は同僚から煙たがられている。
His boorish and obstinate attitude backfired, and he is shunned by his colleagues.
Compound of 無骨 (boorish, rustic) and 一徹 (stubborn, obstinate). The exact historical derivation is uncertain, but the combination emphasizes a person who is both uncouth and stubbornly set in their ways.