n. [ Gr. &unr_; consisting of three layers or plates; &unr_; (see Tri-) + &unr_;, &unr_;, 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. [ 1913 Webster ]
(b) A picture or altarpiece in three compartments. [ 1913 Webster ]