Reredos \Rere"dos\ (r?r"d?s), n. [From rear + F. dos back, L. dorsum. Cf. {Dorsal}.] (Arch.) (a) A screen or partition wall behind an altar. (b) The back of a fireplace. (c) The open hearth, upon which fires were lighted, immediately under the louver, in the center of ancient halls. [Also spelt {reredosse}.] --Fairholt.