The Collaborative International Dictionary of English v.0.48:

Cushion \Cush"ion\ (k[oo^]sh"[u^]n), v. t. [imp. & p. p.
   Cushioned (-[u^]nd); p. pr. & vb. n. Cushioning.]
   1. To seat or place on, or as on a cushion.
      [1913 Webster]

            Many who are cushioned on thrones would have
            remained in obscurity.                --Bolingbroke.
      [1913 Webster]

   2. To furnish with cushions; as, to cushion a chaise.
      [1913 Webster]

   3. To conceal or cover up, as under a cushion.
      [1913 Webster]

   Cushioned hammer, a dead-stroke hammer. See under
      Dead-stroke.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cushion \Cush"ion\ (k??sh"?n), n. [OE. cuischun, quisshen, OF.
   coissin, cuissin, F. coussin, fr. (assumed) LL. culcitinum,
   dim. of L. culcita cushion, mattress, pillow. See Quilt,
   and cf. Counterpoint a coverlet.]
   1. A case or bag stuffed with some soft and elastic material,
      and used to sit or recline upon; a soft pillow or pad.
      [1913 Webster]

            Two cushions stuffed with straw, the seat to raise.
                                                  --Dryden.
      [1913 Webster]

   2. Anything resembling a cushion in properties or use; as:
      (a) a pad on which gilders cut gold leaf;
      (b) a mass of steam in the end of the cylinder of a steam
          engine to receive the impact of the piston;
      (c) the elastic edge of a billiard table.
          [1913 Webster]

   3. A riotous kind of dance, formerly common at weddings; --
      called also cushion dance. --Halliwell.
      [1913 Webster]

   Cushion capital.(Arch.) A capital so sculptured as to
      appear like a cushion pressed down by the weight of its
      entablature.
      (b) A name given to a form of capital, much used in the
          Romanesque style, modeled like a bowl, the upper part
          of which is cut away on four sides, leaving vertical
          faces.

   Cushion star (Zool.) a pentagonal starfish belonging to
      Goniaster, Astrogonium, and other allied genera; -- so
      called from its form.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cushion
    n 1: a mechanical damper; absorbs energy of sudden impulses;
         "the old car needed a new set of shocks" [syn: shock
         absorber, shock, cushion]
    2: the layer of air that supports a hovercraft or similar
       vehicle
    3: a soft bag filled with air or a mass of padding such as
       feathers or foam rubber etc.
    v 1: protect from impact; "cushion the blow" [syn: cushion,
         buffer, soften]

Moby Thesaurus II by Grady Ward, 1.0:

310 Moby Thesaurus words for "cushion":
   abate, absorb, absorb the shock, acoustic tile, aegis,
   afford support, air mattress, allay, alleviate, alleviative,
   alleviator, anesthetize, anodyne, antiknock, appease, arm,
   arm guard, armor, assuage, assuager, back, back up, backstop,
   baffle, baffler, balm, barrier, bear, bear up, bedding, benumb,
   bless, blubber, bolster, bolster up, brace, brattice,
   break the fall, breeze, buffer, buffer state, bulkhead, bulwark,
   bumper, buoy up, butter, buttress, calmative, carry, champion,
   clay, cloak, cloison, collision mat, compass about, contraceptive,
   copyright, cover, cradle, crash helmet, crutch, damp, dampen,
   dampener, damper, dashboard, deaden, deaden the pain, deafen,
   defend, diaphragm, diminish, dissepiment, dividing line,
   dividing wall, division, dodger, dolorifuge, dough, down, dull,
   ease, ease matters, eiderdown, ensure, face mask, feather bed,
   feathers, fence, fend, fender, finger guard, fleece, floss, flue,
   fluff, foam, foment, foot guard, fuse, gag, gentle, give relief,
   give support, goggles, governor, guarantee, guard, guardrail,
   hand guard, handrail, harbor, hard hat, haven, helmet, hold,
   hold up, hushcloth, innerspring mattress, insulate, insulation,
   insure, interlock, interseptum, kapok, keep, keep afloat,
   keep from harm, keep up, knead, knee guard, knuckle guard,
   laminated glass, laxate, lay, lend support, lenitive, lessen,
   life preserver, lifeline, lightning conductor, lightning rod,
   limber, limber up, litter, loosen, lull, mainstay, maintain,
   make safe, mash, mask, massage, mat, mattress, mellow, midriff,
   midsection, milden, mitigate, mitigator, moderator, modulator,
   mollifier, mollify, mudguard, muffle, muffler, mute, muzzle,
   nestle, neutralize, nose guard, numb, offset, pacificator,
   pacifier, pad, padding, palladium, pallet, palliate, palliative,
   panel, paries, partition, party wall, patent, peacemaker, pillow,
   pilot, plump, plush, police, poultice, pour balm into, pour oil on,
   preventive, prop, property line, prophylactic, protect,
   protective clothing, protective umbrella, pudding, puff, pulp,
   putty, quietener, reduce, register, reinforce, relax, relieve,
   restraining hand, ride shotgun for, rubber, rug, safeguard, safety,
   safety glass, safety plug, safety rail, safety shoes,
   safety switch, safety valve, salve, satin, screen, seat belt,
   secure, sedative, separation, septulum, septum, shake up, shelter,
   shield, shin guard, shock absorber, shock pad, shore, shore up,
   shoulder, show consideration, show mercy, show pity, shroud,
   silence cloth, silencer, silk, slacken, slake, sleeping bag, smash,
   soft pedal, soft-pedal, soften, soften the blow, soften up, soothe,
   soother, soothing syrup, sordine, sordino,
   sound-absorbing material, soundproofing, soundproofing insulation,
   sourdine, springs, squash, stabilizer, stay, stop, stupe, subdue,
   subsidize, subvention, sun helmet, supple, support, suppress,
   sustain, swansdown, temperer, tenderize, thistledown, tone down,
   tranquilizer, tune down, umbrella, underbed, underbedding,
   underbrace, undergird, underlie, underpin, underset, underwrite,
   upbear, uphold, upkeep, velvet, wall, wax, windscreen, windshield,
   wiser head, wool, zephyr