Sentence:  A bad <WSD>reredos</WSD> will ruin the best church ever designed; and, although a good <WSD>reredos</WSD> cannot convert a bad church into a good one, it may do much to lessen the offensiveness of its badness. 
Meaning of the word marked with <WSD> tags:  A screen or decoration behind the altar in a church, usually depicting religious iconography or images.