The Collaborative International Dictionary of English v.0.48:

Fleur-de-lis \Fleur`-de-lis`\, n.; pl. Fleurs-de-lis. [F.,
   flower of the lily. Cf. Flower-de-luce, Lily.]
   1. (Bot.) The iris. See Flower-de-luce.
      [1913 Webster]

   2. A conventional flower suggested by the iris, and having a
      form which fits it for the terminal decoration of a
      scepter, the ornaments of a crown, etc. It is also a
      heraldic bearing, and is identified with the royal arms
      and adornments of France.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fleur-de-lis
    n 1: plants with sword-shaped leaves and erect stalks bearing
         bright-colored flowers composed of three petals and three
         drooping sepals [syn: iris, flag, fleur-de-lis,
         sword lily]
    2: (heraldry) charge consisting of a conventionalized
       representation of an iris [syn: fleur-de-lis, fleur-de-
       lys]

Moby Thesaurus II by Grady Ward, 1.0:

146 Moby Thesaurus words for "fleur-de-lis":
   achievement, alerion, animal charge, annulet, argent,
   armorial bearings, armory, arms, azure, badge, badge of office,
   badges, bandeau, bar, bar sinister, baton, bearings, bend,
   bend sinister, billet, blazon, blazonry, bordure, brassard,
   broad arrow, button, cadency mark, canton, cap and gown, chain,
   chain of office, chaplet, charge, chevron, chief, class ring,
   coat of arms, cockade, cockatrice, collar, coronet, crescent,
   crest, cross, cross moline, crown, decoration, device, difference,
   differencing, dress, eagle, emblems, ensigns, ermine, ermines,
   erminites, erminois, escutcheon, falcon, fasces, fess, fess point,
   field, figurehead, file, flanch, fret, fur, fusil, garland,
   griffin, gules, gyron, hammer and sickle, hatchment, helmet,
   heraldic device, heraldry, honor point, impalement, impaling,
   inescutcheon, insignia, label, lapel pin, lion, livery, lozenge,
   mace, mantle, mantling, markings, marshaling, martlet, mascle,
   medal, metal, mortarboard, motto, mullet, nombril point, octofoil,
   old school tie, or, ordinary, orle, pale, paly, pean, pheon, pin,
   purpure, quarter, quartering, regalia, ring, rose, sable, saltire,
   school ring, scutcheon, shamrock, shield, sigillography,
   skull and crossbones, sphragistics, spread eagle, staff,
   subordinary, swastika, tartan, tenne, thistle, tie, tincture,
   torse, tressure, unicorn, uniform, vair, verge, vert, wand, wreath,
   yale