The Collaborative International Dictionary of English v.0.48:

Christmas \Christ"mas\, n. [Christ + mass.]
   An annual church festival (December 25) and in some States a
   legal holiday, in memory of the birth of Christ, often
   celebrated by a particular church service, and also by
   special gifts, greetings, and hospitality.
   [1913 Webster]

   Christmas box.
   (a) A box in which presents are deposited at Christmas.
   (b) A present or small gratuity given to young people and
       servants at Christmas; a Christmas gift.

   Christmas carol, a carol sung at, or suitable for,
      Christmas.

   Christmas day. Same as Christmas.

   Christmas eve, the evening before Christmas.

   Christmas fern (Bot.), an evergreen North American fern
      (Aspidium acrostichoides), which is much used for
      decoration in winter.

   Christmas flower, Christmas rose, the black hellebore, a
      poisonous plant of the buttercup family, which in Southern
      Europe often produces beautiful roselike flowers
      midwinter.

   Christmas tree, a small evergreen tree, set up indoors, to
      be decorated with bonbons, presents, etc., and illuminated
      on Christmas eve.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Christmas
    n 1: period extending from Dec. 24 to Jan. 6 [syn: Christmas,
         Christmastide, Christmastime, Yule, Yuletide,
         Noel]
    2: a Christian holiday celebrating the birth of Christ; a
       quarter day in England, Wales, and Ireland [syn: Christmas,
       Christmas Day, Xmas, Dec 25]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "Christmas":
   Advent, Allhallowmas, Allhallows, Allhallowtide, Annunciation,
   Annunciation Day, Ascension Day, Ash Wednesday, Candlemas,
   Candlemas Day, Carnival, Corpus Christi, Easter, Easter Monday,
   Easter Saturday, Easter Sunday, Eastertide, Ember days, Epiphany,
   Good Friday, Halloween, Hallowmas, Holy Thursday, Holy Week,
   Lady Day, Lammas, Lammas Day, Lammastide, Lent, Lententide,
   Mardi Gras, Martinmas, Maundy Thursday, Michaelmas, Michaelmas Day,
   Michaelmastide, Nativity, Palm Sunday, Pancake Day, Passion Week,
   Pentecost, Quadragesima, Quadragesima Sunday, Septuagesima,
   Shrove Tuesday, Trinity Sunday, Twelfth-day, Twelfth-tide,
   Whit-Tuesday, White Sunday, Whitmonday, Whitsun, Whitsunday,
   Whitsuntide, Whitweek, noel, yule, yuletide



U.S. Gazetteer Places (2000):

Christmas, FL -- U.S. Census Designated Place in Florida
   Population (2000):    1162
   Housing Units (2000): 446
   Land area (2000):     3.572145 sq. miles (9.251812 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    3.572145 sq. miles (9.251812 sq. km)
   FIPS code:            12250
   Located within:       Florida (FL), FIPS 12
   Location:             28.532428 N, 80.993956 W
   ZIP Codes (1990):     32709
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Christmas, FL
    Christmas