Source : Webster's Revised Unabridged Dictionary (1913)

Mansion \Man"sion\, v. i.
   To dwell; to reside. [Obs.] --Mede.

Mansion \Man"sion\, n. [OF. mansion, F. maison, fr. L. mansio a
   staying, remaining, a dwelling, habitation, fr. manere,
   mansum, to stay, dwell; akin to Gr. ?. Cf. {Manse}, {Manor},
   {Menagerie}, {Menial}, {Permanent}.]
   1. A dwelling place, -- whether a part or whole of a house or
      other shelter. [Obs.]

            In my Father's house are many mansions. --John xiv.
                                                  2.

            These poets near our princes sleep, And in one grave
            their mansions keep.                  --Den?am.

   2. The house of the lord of a manor; a manor house; hence:
      Any house of considerable size or pretension.

   3. (Astrol.) A twelfth part of the heavens; a house. See 1st
      {House}, 8. --Chaucer.

   4. The place in the heavens occupied each day by the moon in
      its monthly revolution. [Obs.]

            The eight and twenty mansions That longen to the
            moon.                                 --Chaucer.

   {Mansion house}, the house in which one resides;
      specifically, in London and some other cities, the
      official residence of the Lord Mayor. --Blackstone.

Source : WordNet®

mansion
     n 1: (astrology) one of 12 equal areas into which the zodiac is
          divided [syn: {sign of the zodiac}, {star sign}, {sign},
           {house}, {planetary house}]
     2: a large and imposing house [syn: {mansion house}, {manse}, {hall},
         {residence}]