The Collaborative International Dictionary of English v.0.48:

Shield \Shield\, n. [OE. sheld, scheld, AS. scield, scild,
   sceld, scyld; akin to OS. scild, OFries. skeld, D. & G.
   schild, OHG. scilt, Icel. skj["o]ldr, Sw. sk["o]ld, Dan.
   skiold, Goth. skildus; of uncertain origin. Cf. Sheldrake.]
   1. A broad piece of defensive armor, carried on the arm, --
      formerly in general use in war, for the protection of the
      body. See Buckler.
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            Now put your shields before your hearts and fight,
            With hearts more proof than shields.  --Shak.
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   2. Anything which protects or defends; defense; shelter;
      protection. "My council is my shield." --Shak.
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   3. Figuratively, one who protects or defends.
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            Fear not, Abram; I am thy shield, and thy exceeding
            great reward.                         --Gen. xv. 1.
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   4. (Bot.) In lichens, a Hardened cup or disk surrounded by a
      rim and containing the fructification, or asci.
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   5. (Her.) The escutcheon or field on which are placed the
      bearings in coats of arms. Cf. Lozenge. See Illust. of
      Escutcheon.
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   6. (Mining & Tunneling) A framework used to protect workmen
      in making an adit under ground, and capable of being
      pushed along as excavation progresses.
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   7. A spot resembling, or having the form of, a shield.
      "Bespotted as with shields of red and black." --Spenser.
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   8. A coin, the old French crown, or ['e]cu, having on one
      side the figure of a shield. [Obs.] --Chaucer.
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   Shield fern (Bot.), any fern of the genus Aspidium, in
      which the fructifications are covered with shield-shaped
      indusia; -- called also wood fern. See Illust. of
      Indusium.
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The Collaborative International Dictionary of English v.0.48:

Shield \Shield\, v. t. [imp. & p. p. Shielded; p. pr. & vb. n.
   Shielding.] [AS. scidan, scyldan. See Shield, n.]
   1. To cover with, or as with, a shield; to cover from danger;
      to defend; to protect from assault or injury.
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            Shouts of applause ran ringing through the field,
            To see the son the vanquished father shield.
                                                  --Dryden.
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            A woman's shape doth shield thee.     --Shak.
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   2. To ward off; to keep off or out.
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            They brought with them their usual weeds, fit to
            shield the cold to which they had been inured.
                                                  --Spenser.
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   3. To avert, as a misfortune; hence, as a supplicatory
      exclamation, forbid! [Obs.]
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            God shield that it should so befall.  --Chaucer.
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            God shield I should disturb devotion! --Shak.
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WordNet (r) 3.0 (2006):

shield
    n 1: a protective covering or structure
    2: armor carried on the arm to intercept blows [syn: shield,
       buckler]
    3: hard outer covering or case of certain organisms such as
       arthropods and turtles [syn: carapace, shell, cuticle,
       shield]
    v 1: protect, hide, or conceal from danger or harm [syn:
         shield, screen]
    2: hold back a thought or feeling about; "She is harboring a
       grudge against him" [syn: harbor, harbour, shield]

Moby Thesaurus II by Grady Ward, 1.0:

273 Moby Thesaurus words for "shield":
   achievement, advocate, aegis, alerion, animal charge, annulet,
   apply to, argent, arm, arm guard, armament, armature, armor,
   armor plate, armorial bearings, armory, arms, azure, backstop,
   bandeau, bar, bar sinister, baton, bearings, bend, bend sinister,
   billet, blanket, blazon, blazonry, bless, block, body armor,
   bordure, broad arrow, buckler, buffer, bulletproof vest, bulwark,
   bumper, cadency mark, canopy, canton, chain armor, chain mail,
   chamber, champion, chaplet, charge, chevron, chief, chitin, cloak,
   clothe, cloud, coat, coat of arms, coat of mail, cockatrice,
   compass about, contraceptive, cope, copyright, coronet, cortex,
   cover, cover up, coverage, covering, covert, coverture, cowl,
   cowling, crash helmet, crescent, crest, cross, cross moline, crown,
   curtain, cushion, dashboard, defence, defend, device, difference,
   differencing, dodger, drape, drapery, eagle, eclipse, elytron,
   ensure, episperm, ermine, ermines, erminites, erminois, escutcheon,
   face mask, falcon, fence, fend, fender, fess, fess point, field,
   file, film, finger guard, flanch, flank, fleur-de-lis, foot guard,
   fret, fur, fuse, fusil, garland, goggles, governor, griffin,
   guarantee, guard, guard against, guardrail, guise, gules, gyron,
   habergeon, hand guard, handrail, hanging, harbor, hard hat,
   harness, hatchment, hauberk, haven, helmet, heraldic device,
   honor point, hood, house, housing, impalement, impaling,
   inescutcheon, insulation, insure, interlock, keep, keep from harm,
   knee guard, knuckle guard, label, laminated glass, lay on,
   lay over, life preserver, lifeline, lightning conductor,
   lightning rod, lion, lorica, lorication, lozenge, mail, make safe,
   mantle, mantling, marshaling, martlet, mascle, mask, metal, motto,
   mudguard, muffle, mullet, needles, nestle, nombril point,
   nose guard, obduce, obscure, occult, octofoil, or, ordinary, orle,
   overlay, overspread, pad, padding, pale, pall, palladium, paly,
   panoply, patent, pean, pericarp, pheon, pilot, plate, plate armor,
   police, preventive, prophylactic, protect, protection,
   protective clothing, protective covering, protective umbrella,
   purpure, put on, quarter, quartering, register, ride shotgun for,
   roof, rose, sable, safeguard, safety, safety glass, safety plug,
   safety rail, safety shoes, safety switch, safety valve, saltire,
   screen, scum, scutcheon, scute, scutum, seat belt, secure,
   security, shell, shelter, shin guard, shroud, spines, spread eagle,
   spread over, subordinary, suit of armor, sun helmet, superimpose,
   superpose, tenne, test, testa, thick skin, tincture, torse,
   tressure, umbrella, underwrite, unicorn, vair, veil, vert,
   vestment, ward, windscreen, windshield, wreath, yale



Easton's 1897 Bible Dictionary:

Shield
   used in defensive warfare, varying at different times and under
   different circumstances in size, form, and material (1 Sam.
   17:7; 2 Sam. 1:21; 1 Kings 10:17; 1 Chr. 12:8, 24, 34; Isa.
   22:6; Ezek. 39:9; Nahum 2:3).

     Used figuratively of God and of earthly princes as the
   defenders of their people (Gen. 15:1; Deut. 33:29; Ps. 33:20;
   84:11). Faith is compared to a shield (Eph. 6:16).

     Shields were usually "anointed" (Isa. 21:5), in order to
   preserve them, and at the same time make the missiles of the
   enemy glide off them more easily.