noun
Refers to a set of three matching items, especially in art or decorative contexts such as a triptych of paintings or a set of three hanging scrolls.
床の間に三幅対の掛け軸が飾ってある。
A set of three hanging scrolls is displayed in the alcove.
三つ組 is a more general term for a set of three, while 三幅対 specifically refers to a matching set of three art pieces or scrolls.
Compound of 三 (three), 幅 (counter for scrolls or paintings), and 対 (pair, set). The term originally described a set of three hanging scrolls displayed together.