n. In architecture, the back of a fireplace, or of an open fire-hearth, as commonly used in domestic halls of medieval times and the Renaissance; the iron plate often forming the back of a fireplace in which andirons are used.n. A screen or a decorated part of the wall behind an altar in a church, especially when the altar does not stand free, but against the wall; an altarpiece. Compare altarpiece and retable.n. In medieval armor, same as backpiece.