noun
A somewhat old-fashioned or literary term for an uncultured, rough-mannered person, often from the countryside. Can be used humorously or insultingly.
彼は都会に出てきたばかりの無骨者だ。
He's a rustic who just came to the city.
あの無骨者に礼儀を期待するな。
Don't expect manners from that boor.
Compound of 無骨 (boorish, rustic) and 者 (person). The exact historical derivation of 無骨 is uncertain, but it is conventionally associated with the idea of lacking refinement.