The Collaborative International Dictionary of English v.0.48:

Fillet \Fil"let\, n. [OE. filet, felet, fr. OF. filet thread,
   fillet of meat, dim. of fil a thread, fr. L. filum. See
   Fille a row.]
   1. A little band, especially one intended to encircle the
      hair of the head.
      [1913 Webster]

            A belt her waist, a fillet binds her hair. --Pope.
      [1913 Webster]

   2. (Cooking) A piece of lean meat without bone; sometimes, a
      long strip rolled together and tied.
      [1913 Webster]

   Note: A fillet of beef is the under side of the sirlom; also
         called tenderloin. A fillet of veal or mutton is the
         fleshy part of the thigh. A fillet of fish is a slice
         of flat fish without bone. "Fillet of a fenny snake."
         --Shak.
         [1913 Webster]

   3. A thin strip or ribbon; esp.:
      (a) A strip of metal from which coins are punched.
      (b) A strip of card clothing.
      (c) A thin projecting band or strip.
          [1913 Webster]

   4. (Mach.) A concave filling in of a re["e]ntrant angle where
      two surfaces meet, forming a rounded corner.
      [1913 Webster]

   5. (Arch.) A narrow flat member; especially, a flat molding
      separating other moldings; a reglet; also, the space
      between two flutings in a shaft. See Illust. of Base,
      and Column.
      [1913 Webster]

   6. (Her.) An ordinary equaling in breadth one fourth of the
      chief, to the lowest portion of which it corresponds in
      position.
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   7. (Mech.) The thread of a screw.
      [1913 Webster]

   8. A border of broad or narrow lines of color or gilt.
      [1913 Webster]

   9. The raised molding about the muzzle of a gun.
      [1913 Webster]

   10. Any scantling smaller than a batten.
       [1913 Webster]

   11. (Anat.) A fascia; a band of fibers; applied esp. to
       certain bands of white matter in the brain.
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   12. (Man.) The loins of a horse, beginning at the place where
       the hinder part of the saddle rests.
       [1913 Webster]

   Arris fillet. See under Arris.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Fillet \Fil"let\, v. t. [imp. & p. p. Filleted; p. pr. & vb.
   n. Filleting.]
   To bind, furnish, or adorn with a fillet.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fillet
    n 1: a boneless steak cut from the tenderloin of beef [syn:
         fillet, filet]
    2: a longitudinal slice or boned side of a fish [syn: fillet,
       filet, fish fillet, fish filet]
    3: a bundle of sensory nerve fibers going to the thalamus [syn:
       lemniscus, fillet]
    4: a narrow headband or strip of ribbon worn as a headband [syn:
       taenia, tenia, fillet]
    5: fastener consisting of a narrow strip of welded metal used to
       join steel members [syn: fillet, stopping]
    v 1: decorate with a lace of geometric designs [syn: fillet,
         filet]
    2: cut into filets; "filet the fish" [syn: fillet, filet]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "fillet":
   Mystik tape, Scotch tape, adhesive tape, anklet, armlet, band,
   bandage, bandeau, batten, belt, bracelet, cellophane tape,
   cincture, cingulum, cloth tape, collar, collarband, earring,
   ecliptic, equator, fascia, finger ring, friction tape, girdle,
   girt, girth, great circle, hoop, lath, ligula, ligule, list,
   masking tape, neckband, necklace, nose ring, plank, plastic tape,
   quoit, ribband, ribbon, ring, shred, slat, slip, spill, spline,
   strake, strap, strip, stripe, strop, taenia, tape, tape measure,
   tapeline, ticker tape, wristband, wristlet, zodiac, zone