The Collaborative International Dictionary of English v.0.48:

Topknot \Top"knot`\, n.
   1. A crest or knot of feathers upon the head or top, as of a
      bird; also, an ornamental knot worn on top of the head, as
      by women.
      [1913 Webster]

            A great, stout servant girl, with cheeks as red as
            her topknot.                          --Sir W.
                                                  Scott.
      [1913 Webster]

   2. (Zool.) A small Europen flounder (Rhoumbus punctatus).
      The name is also applied to allied species.
      [1913 Webster]

WordNet (r) 3.0 (2006):

topknot
    n 1: headdress consisting of a decorative ribbon or bow worn in
         the hair
    2: showy crest or knot of hair or feathers

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "topknot":
   braid, bun, cap, capsheaf, caput, chignon, coil, crest, crown, cue,
   feather, hackle, head, heading, headpiece, knot, panache, pigtail,
   pinhead, pinion, plait, plume, plumule, queue, quill, rattail,
   scapular, tail, tuft, twist