Source : Webster's Revised Unabridged Dictionary (1913)

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}.

   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.

Source : WordNet®

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}, {sword lily}]
     2: (heraldry) charge consisting of a conventionalized
        representation of an iris [syn: {fleur-de-lys}]
     [also: {fleurs-de-lis} (pl)]

fleurs-de-lis
     See {fleur-de-lis}