The Collaborative International Dictionary of English v.0.48:

Feather \Feath"er\ (f[e^][th]"[~e]r), n. [OE. fether, AS.
   fe[eth]er; akin to D. veder, OHG. fedara, G. feder, Icel.
   fj["o][eth]r, Sw. fj[aum]der, Dan. fj[ae]der, Gr. ptero`n
   wing, feather, pe`tesqai to fly, Skr. pattra wing, feather,
   pat to fly, and prob. to L. penna feather, wing. [root]76,
   248. Cf. Pen a feather.]
   1. One of the peculiar dermal appendages, of several kinds,
      belonging to birds, as contour feathers, quills, and down.
      [1913 Webster]

   Note: An ordinary feather consists of the quill or hollow
         basal part of the stem; the shaft or rachis, forming
         the upper, solid part of the stem; the vanes or webs,
         implanted on the rachis and consisting of a series of
         slender lamin[ae] or barbs, which usually bear
         barbules, which in turn usually bear barbicels and
         interlocking hooks by which they are fastened together.
         See Down, Quill, Plumage.

   2. Kind; nature; species; -- from the proverbial phrase,
      "Birds of a feather," that is, of the same species. [R.]
      [1913 Webster]

            I am not of that feather to shake off
            My friend when he must need me.       --Shak.
      [1913 Webster]

   3. The fringe of long hair on the legs of the setter and some
      other dogs.
      [1913 Webster]

   4. A tuft of peculiar, long, frizzly hair on a horse.
      [1913 Webster]

   5. One of the fins or wings on the shaft of an arrow.
      [1913 Webster]

   6. (Mach. & Carp.) A longitudinal strip projecting as a fin
      from an object, to strengthen it, or to enter a channel in
      another object and thereby prevent displacement sidwise
      but permit motion lengthwise; a spline.
      [1913 Webster]

   7. A thin wedge driven between the two semicylindrical parts
      of a divided plug in a hole bored in a stone, to rend the
      stone. --Knight.
      [1913 Webster]

   8. The angular adjustment of an oar or paddle-wheel float,
      with reference to a horizontal axis, as it leaves or
      enters the water.
      [1913 Webster]

   Note: Feather is used adjectively or in combination, meaning
         composed of, or resembling, a feather or feathers; as,
         feather fan, feather-heeled, feather duster.
         [1913 Webster]

   Feather alum (Min.), a hydrous sulphate of alumina,
      resulting from volcanic action, and from the decomposition
      of iron pyrites; -- called also halotrichite. --Ure.

   Feather bed, a bed filled with feathers.

   Feather driver, one who prepares feathers by beating.

   Feather duster, a dusting brush of feathers.

   Feather flower, an artifical flower made of feathers, for
      ladies' headdresses, and other ornamental purposes.

   Feather grass (Bot.), a kind of grass (Stipa pennata)
      which has a long feathery awn rising from one of the
      chaffy scales which inclose the grain.

   Feather maker, one who makes plumes, etc., of feathers,
      real or artificial.

   Feather ore (Min.), a sulphide of antimony and lead,
      sometimes found in capillary forms and like a cobweb, but
      also massive. It is a variety of Jamesonite.

   Feather shot, or Feathered shot (Metal.), copper
      granulated by pouring into cold water. --Raymond.

   Feather spray (Naut.), the spray thrown up, like pairs of
      feathers, by the cutwater of a fast-moving vessel.

   Feather star. (Zool.) See Comatula.

   Feather weight. (Racing)
      (a) Scrupulously exact weight, so that a feather would
          turn the scale, when a jockey is weighed or weighted.
      (b) The lightest weight that can be put on the back of a
          horse in racing. --Youatt.
      (c) In wrestling, boxing, etc., a term applied to the
          lightest of the classes into which contestants are
          divided; -- in contradistinction to light weight,
          middle weight, and heavy weight.

   A feather in the cap an honour, trophy, or mark of
      distinction. [Colloq.]

   To be in full feather, to be in full dress or in one's best
      clothes. [Collog.]

   To be in high feather, to be in high spirits. [Collog.]

   To cut a feather.
      (a) (Naut.) To make the water foam in moving; in allusion
          to the ripple which a ship throws off from her bows.
      (b) To make one's self conspicuous. [Colloq.]

   To show the white feather, to betray cowardice, -- a white
      feather in the tail of a cock being considered an
      indication that he is not of the true game breed.
      [1913 Webster]

WordNet (r) 3.0 (2006):

feather bed
    n 1: a mattress stuffed with feathers [syn: feather bed,
         featherbed]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "feather bed":
   blubber, breeze, butter, clay, cushion, dough, down, eiderdown,
   feathers, fleece, floss, flue, fluff, foam, kapok, pillow, plush,
   pudding, puff, putty, rubber, satin, silk, swansdown, thistledown,
   velvet, wax, wool, zephyr