The Collaborative International Dictionary of English v.0.48:

Comforter \Com"fort*er\, n.
   1. One who administers comfort or consolation.
      [1913 Webster]

            Let no comforter delight mine ear
            But such a one whose wrongs do suit with mine.
                                                  --Shak.
      [1913 Webster]

   2. (Script.) The Holy Spirit, -- referring to his office of
      comforting believers.
      [1913 Webster]

            But the Comforter, which is the Holy Ghost, whom the
            Father will send in my name, he shall teach you all
            things.                               --John xiv.
                                                  26.
      [1913 Webster]

   3. A knit woolen tippet, long and narrow. [U. S.]
      [1913 Webster]

            The American schoolboy takes off his comforter and
            unbuttons his jacket before going in for a snowball
            fight.                                --Pop. Sci.
                                                  Monthly.
      [1913 Webster]

   4. A wadded bedquilt; a comfortable. [U. S.]
      [1913 Webster]

   Job's comforter, a boil. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

comforter
    n 1: commiserates with someone who has had misfortune [syn:
         sympathizer, sympathiser, comforter]
    2: a person who reduces the intensity (e.g., of fears) and calms
       and pacifies; "a reliever of anxiety"; "an allayer of fears"
       [syn: reliever, allayer, comforter]
    3: bedding made of two layers of cloth filled with stuffing and
       stitched together [syn: quilt, comforter, comfort,
       puff]
    4: device used for an infant to suck or bite on [syn:
       comforter, pacifier, baby's dummy, teething ring]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "comforter":
   afghan, bed linen, bedclothes, bedcover, bedding, bedsheet,
   bedspread, blanket, buffalo robe, case, clothes, comfort, consoler,
   contour sheet, counterpane, cover, coverlet, coverlid, eiderdown,
   encourager, fitted sheet, lap robe, linen, paraclete,
   patchwork quilt, pillow slip, pillowcase, puff, quilt, robe, rug,
   sheet, sheeting, slip, solacer, spread



Easton's 1897 Bible Dictionary:

Comforter
   the designation of the Holy Ghost (John 14:16, 26; 15:26; 16:7;
   R.V. marg., "or Advocate, or Helper; Gr. paracletos"). The same
   Greek word thus rendered is translated "Advocate" in 1 John 2:1
   as applicable to Christ. It means properly "one who is summoned
   to the side of another" to help him in a court of justice by
   defending him, "one who is summoned to plead a cause."
   "Advocate" is the proper rendering of the word in every case
   where it occurs.

     It is worthy of notice that although Paul nowhere uses the
   word paracletos, he yet presents the idea it embodies when he
   speaks of the "intercession" both of Christ and the Spirit (Rom.
   8:27, 34).