n. - Anything consisting of two leaves.
n. - A writing tablet consisting of two leaves of rigid material connected by hinges and shutting together so as to protect the writing within.
n. - A picture or series of pictures painted on two tablets connected by hinges. See Triptych.
n. - A double catalogue, containing in one part the names of living, and in the other of deceased, ecclesiastics and benefactors of the church; a catalogue of saints.