What does altar mean?
The definition of altar
Al”tar, n.
Etym: [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. 20.
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 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.