The Collaborative International Dictionary of English v.0.48:
Altar \Al"tar\, n. [OE. alter, auter, autier, fr. L. altare, pl.
altaria, altar, prob. fr. altus high: cf. OF. alter, autier,
F. autel. Cf. Altitude.]
1. A raised structure (as a square or oblong erection of
stone or wood) on which sacrifices are offered or incense
burned to a deity.
Noah builded an altar unto the Lord. --Gen. viii.
2. In the Christian church, a construction of stone, wood, or
other material for the celebration of the Holy Eucharist;
the communion table.
Note: Altar is much used adjectively, or as the first part of
a compound; as, altar bread or altar-bread.
Altar cloth or
Altar-cloth, the cover for an altar in a Christian church,
usually richly embroidered.
Altar cushion, a cushion laid upon the altar in a Christian
church to support the service book.
Altar frontal. See Frontal.
Altar rail, the railing in front of the altar or communion
Altar screen, a wall or partition built behind an altar to
protect it from approach in the rear.
Altar tomb, a tomb resembling an altar in shape, etc.
Family altar, place of family devotions.
To lead (as a bride) to the altar, to marry; -- said of a