NOUN (2)

1. a small crown; usually indicates a high rank but below that of sovereign;

2. margin between the skin of the pastern and the horn of the hoof;

The Collaborative International Dictionary of English v.0.48:

Coronet \Cor"o*net\ (k?r"?-n?t), n. [Dim. of OE. corone crown;
   cf. OF. coronete. See Crown, and cf. Crownet, Cronet.]
   [1913 Webster]
   1. An ornamental or honorary headdress, having the shape and
      character of a crown; particularly, a crown worn as the
      mark of high rank lower than sovereignty. The word is used
      by Shakespeare to denote also a kingly crown.
      [1913 Webster]

            Without a star, a coronet, or garter. --Goldsmith.
      [1913 Webster]

   Note: The coronet of the Prince of Wales consist of a circlet
         of gold with four crosses patt['e]e around the edge
         between as many fleurs-de-lis. The center crosses are
         connected by an arch which is surmounted by a globe or
         cross. The coronet of a British duke is adorned with
         strawberry leaves; that of a marquis has leaves with
         pearls interposed; that of an earl raises the pearls
         above the leaves; that of a viscount is surrounded with
         pearls only; that of a baron has only four pearls.
         [1913 Webster]

   2. (Far.) The upper part of a horse's hoof, where the horn
      terminates in skin. --James White.
      [1913 Webster]

   3. (Anc. Armor) The iron head of a tilting spear; a coronel.
      --Crose.
      [1913 Webster]

WordNet (r) 3.0 (2006):

coronet
    n 1: a small crown; usually indicates a high rank but below that
         of sovereign
    2: margin between the skin of the pastern and the horn of the
       hoof