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.
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            Noah builded an altar unto the Lord.  --Gen. viii.
                                                  20.
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   2. In the Christian church, a construction of stone, wood, or
      other material for the celebration of the Holy Eucharist;
      the communion table.
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   Note: Altar is much used adjectively, or as the first part of
         a compound; as, altar bread or altar-bread.
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   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
      table.

   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
      woman.
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