na-adjective, noun
boorish; uncouth; rustic; clumsy; brusque
Describes a person or manner that is rough, unrefined, and lacking social polish. Often carries a nuance of being straightforward and unsophisticated rather than intentionally rude. Can be used for appearance, behavior, or speech.
彼は武骨だが、心は優しい。
He is rough around the edges, but he has a kind heart.
武骨な手つきで茶碗
He held out the teacup with clumsy, unrefined hands.
粗野 is more strongly negative, implying crudeness or vulgarity, while 武骨 suggests a lack of polish that may be seen as endearingly rustic or straightforward.
無骨者 is a noun meaning a boorish person, derived from 武骨. It explicitly refers to a person, whereas 武骨 can describe both people and their manner.
The word is composed of 武 (martial) or 無 (without) and 骨 (bone, frame). The exact derivation is uncertain, but it likely originally referred to someone with a rough, unpolished frame or manner, akin to an unsophisticated warrior.