The Collaborative International Dictionary of English v.0.48:

Retable \Re*ta"ble\ (r[-e]*t[=a]"b'l), n. (Eccl.)
   A shelf behind the altar, for display of lights, vases of
   flowers, etc.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "retable":
   Communion table, altar, altar carpet, altar desk, altar facing,
   altar of prothesis, altar rail, altar side, altar slab,
   altar stair, altar stone, altarpiece, ancona, beam-end, bomos,
   chancel table, corbel, credence, eschara, frontal, gradin, gradino,
   hestia, hob, holy table, ledge, mantel, mantelshelf, mensal,
   missal stand, predella, prothesis, retablo, rood altar, scrobis,
   shelf, shoulder, superaltar