The Collaborative International Dictionary of English v.0.48:

Harness \Har"ness\ (-n[e^]s), n. [OE. harneis, harnes, OF.
   harneis, F. harnais, harnois; of Celtic origin; cf. Armor.
   harnez old iron, armor, W. haiarn iron, Armor. houarn, Ir.
   iarann, Gael. iarunn. Cf. Iron.]
   1. Originally, the complete dress, especially in a military
      sense, of a man or a horse; hence, in general, armor.
      [1913 Webster]

            At least we'll die with harness on our back. --Shak.
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   2. The equipment of a draught or carriage horse, for drawing
      a wagon, coach, chaise, etc.; gear; tackling.
      [1913 Webster]

   3. The part of a loom comprising the heddles, with their
      means of support and motion, by which the threads of the
      warp are alternately raised and depressed for the passage
      of the shuttle.
      [1913 Webster]

   To die in harness, to die with armor on; hence,
      colloquially, to die while actively engaged in work or
      duty.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Harness \Har"ness\, v. t. [imp. & p. p. Harnessed (-n[e^]st);
   p. pr. & vb. n. Harnessing.] [OE. harneisen; cf. F.
   harnacher, OF. harneschier.]
   1. To dress in armor; to equip with armor for war, as a
      horseman; to array.
      [1913 Webster]

            Harnessed in rugged steel.            --Rowe.
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            A gay dagger,
            Harnessed well and sharp as point of spear.
                                                  --Chaucer.
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   2. Fig.: To equip or furnish for defense. --Dr. H. More.
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   3. To make ready for draught; to equip with harness, as a
      horse. Also used figuratively.
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            Harnessed to some regular profession. --J. C.
                                                  Shairp.
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   Harnessed antelope. (Zool.) See Guib.

   Harnessed moth (Zool.), an American bombycid moth (Arctia
      phalerata of Harris), having, on the fore wings, stripes
      and bands of buff on a black ground.
      [1913 Webster]

WordNet (r) 3.0 (2006):

harness
    n 1: a support consisting of an arrangement of straps for
         holding something to the body (especially one supporting a
         person suspended from a parachute)
    2: stable gear consisting of an arrangement of leather straps
       fitted to a draft animal so that it can be attached to and
       pull a cart
    v 1: put a harness; "harness the horse" [syn: harness,
         tackle] [ant: unharness]
    2: exploit the power of; "harness natural forces and resources"
    3: control and direct with or as if by reins; "rein a horse"
       [syn: harness, rein in, draw rein, rein]
    4: keep in check; "rule one's temper" [syn: rule, harness,
       rein]

Moby Thesaurus II by Grady Ward, 1.0:

115 Moby Thesaurus words for "harness":
   accouterments, armature, armor, armor plate, back band, backstrap,
   bearing rein, bed, bed down, bellyband, bit, blinders, blinds,
   body armor, break, breeching, bridle, brolly, brush, buckler,
   bulletproof vest, caparison, cavesson, chain armor, chain mail,
   checkrein, cheekpiece, chinband, chute, cinch, coat of mail,
   collar, cortex, couple, crownband, crupper, curb, curry, currycomb,
   drench, drogue chute, feed, fetter, fodder, furnishings,
   gag swivel, gentle, getup, girth, groom, habergeon, hackamore,
   halter, hames, hametugs, handle, hauberk, headgear, headstall,
   hip straps, hitch, hitch up, hook up, jaquima, jerk line, lines,
   litter, livery, mail, manage, martingale, milk, needles, noseband,
   outfit, pack, panoply, parachute, parachute jump, plate armor,
   pole strap, protective covering, reins, ribbons, rig, rub down,
   saddle, shaft tug, shell, shield, shroud lines, side check,
   sky dive, snaffle, spines, suit of armor, surcingle, tack, tackle,
   tame, tend, tether, thick skin, things, train, trappings,
   trousseau, tug, turnout, umbrella, vent, wardrobe, water,
   winker braces, yoke



Easton's 1897 Bible Dictionary:

Harness
   (1.) Heb. 'asar, "to bind;" hence the act of fastening animals
   to a cart (1 Sam. 6:7, 10; Jer. 46:4, etc.).

     (2.) An Old English word for "armour;" Heb. neshek (2 Chr.
   9:24).

     (3.) Heb. shiryan, a coat of mail (1 Kings 22:34; 2 Chr.
   18:33; rendered "breastplate" in Isa. 59:17).

     (4.) The children of Israel passed out of Egypt "harnessed"
   (Ex. 13:18), i.e., in an orderly manner, and as if to meet a
   foe. The word so rendered is probably a derivative from Hebrew
   _hamesh_ (i.e., "five"), and may denote that they went up in
   five divisions, viz., the van, centre, two wings, and
   rear-guard.