The Collaborative International Dictionary of English v.0.48:

Coat \Coat\ (k[=o]t; 110), n. [OF. cote, F. cotte, petticoat,
   cotte d'armes coat of arms, cotte de mailles coat of mail,
   LL. cota, cotta, tunic, prob. of German origin; cf. OHG.
   chozzo coarse mantle, G. klotze, D. kot, hut, E. cot. Cf.
   Cot a hut.]
   1. An outer garment fitting the upper part of the body;
      especially, such a garment worn by men.
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            Let each
            His adamantine coat gird well.        --Milton.
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   2. A petticoat. [Obs.] "A child in coats." --Locke.
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   3. The habit or vesture of an order of men, indicating the
      order or office; cloth.
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            Men of his coat should be minding their prayers.
                                                  --Swift.
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            She was sought by spirits of richest coat. --Shak.
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   4. An external covering like a garment, as fur, skin, wool,
      husk, or bark; as, the horses coats were sleek.
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            Fruit of all kinds, in coat
            Rough or smooth rined, or bearded husk, or shell.
                                                  --Milton.
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   5. A layer of any substance covering another; a cover; a
      tegument; as, the coats of the eye; the coats of an onion;
      a coat of tar or varnish.
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   6. Same as Coat of arms. See below.
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            Hark, countrymen! either renew the fight,
            Or tear the lions out of England's coat. --Shak.
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   7. A coat card. See below. [Obs.]
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            Here's a trick of discarded cards of us! We were
            ranked with coats as long as old master lived.
                                                  --Massinger.
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   Coat armor. See under Armor.

   Coat of arms (Her.), a translation of the French cotte
      d'armes, a garment of light material worn over the armor
      in the 15th and 16th centuries. This was often charged
      with the heraldic bearings of the wearer. Hence, an
      heraldic achievement; the bearings of any person, taken
      together.

   Coat card, a card bearing a coated figure; the king, queen,
      or knave of playing cards. "`I am a coat card indeed.'
      `Then thou must needs be a knave, for thou art neither
      king nor queen.'" --Rowley.

   Coat link, a pair of buttons or studs joined by a link, to
      hold together the lappels of a double-breasted coat; or a
      button with a loop for a single-breasted coat.

   Coat of mail, a defensive garment of chain mail. See Chain
      mail, under Chain.

   Mast coat (Naut.), a piece of canvas nailed around a mast,
      where it passes through the deck, to prevent water from
      getting below.

   Sail coat (Naut.), a canvas cover laced over furled sails,
      and the like, to keep them dry and clean.
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WordNet (r) 3.0 (2006):

coat of arms
    n 1: the official symbols of a family, state, etc. [syn: coat
         of arms, arms, blazon, blazonry]

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "coat of arms":
   achievement, alerion, animal charge, annulet, argent,
   armorial bearings, armory, arms, azure, bandeau, bar, bar sinister,
   baton, bearings, bend, bend sinister, billet, blazon, blazonry,
   bordure, broad arrow, cadency mark, canton, chaplet, charge,
   chevron, chief, cockatrice, coronet, crescent, crest, cross,
   cross moline, crown, device, difference, differencing, eagle,
   ermine, ermines, erminites, erminois, escutcheon, falcon, fess,
   fess point, field, file, flanch, fleur-de-lis, fret, fur, fusil,
   garland, griffin, gules, gyron, hatchment, helmet, heraldic device,
   honor point, impalement, impaling, inescutcheon, label, lion,
   lozenge, mantling, marshaling, martlet, mascle, metal, motto,
   mullet, nombril point, octofoil, or, ordinary, orle, pale, paly,
   pean, pheon, purpure, quarter, quartering, rose, sable, saltire,
   scutcheon, shield, spread eagle, subordinary, tenne, tincture,
   torse, tressure, unicorn, vair, vert, wreath, yale