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]