n. 三张相联的图画, 三幅一联

[ noun ]
art consisting of a painting or carving (especially an altarpiece) on three panels (usually hinged together)
<noun.artifact>

Triptych \Trip"tych\, n. [Gr. ? consisting of three layers or
plates; ? (see {Tri-}) + ?, ?, a fold, layer.]
Anything in three parts or leaves. Specifically:
(a) A writing tablet in three parts, two of which fold over
on the middle part.
(b) A picture or altarpiece in three compartments.