The Collaborative International Dictionary of English v.0.48:

Annulet \An"nu*let\, n. [Dim. of annulus.]
   1. A little ring. --Tennyson.
      [1913 Webster]

   2. (Arch.) A small, flat fillet, encircling a column, etc.,
      used by itself, or with other moldings. It is used,
      several times repeated, under the Doric capital.
      [1913 Webster]

   3. (Her.) A little circle borne as a charge.
      [1913 Webster]

   4. (Zool.) A narrow circle of some distinct color on a
      surface or round an organ.
      [1913 Webster]

WordNet (r) 3.0 (2006):

annulet
    n 1: (heraldry) a charge in the shape of a circle; "a hollow
         roundel" [syn: annulet, roundel]
    2: molding in the form of a ring; at top of a column [syn:
       annulet, bandelet, bandelette, bandlet, square and
       rabbet]
    3: a small ring

Moby Thesaurus II by Grady Ward, 1.0:

108 Moby Thesaurus words for "annulet":
   achievement, alerion, animal charge, 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,
   circlet, coat of arms, cockatrice, coronet, crescent, crest, cross,
   cross moline, crown, device, difference, differencing, eagle,
   ermine, ermines, erminites, erminois, escutcheon, eye, eyelet,
   falcon, fess, fess point, field, file, flanch, fleur-de-lis, fret,
   fur, fusil, garland, griffin, grommet, 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, ringlet, rose, roundlet, sable, saltire, scutcheon,
   shield, spread eagle, subordinary, tenne, tincture, torse,
   tressure, unicorn, vair, vert, wreath, yale