The Collaborative International Dictionary of English v.0.48:

hackle \hac"kle\ (h[a^]k"k'l), n. [See Heckle, and cf.
   Hatchel.]
   [1913 Webster]
   1. A comb for dressing flax, raw silk, etc.; a hatchel.
      [1913 Webster]

   2. Any flimsy substance unspun, as raw silk.
      [1913 Webster]

   3. One of the peculiar, long, narrow feathers on the neck of
      fowls, most noticeable on the cock, -- often used in
      making artificial flies; hence, any feather so used.
      [1913 Webster]

   4. An artificial fly for angling, made of feathers.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hackle \Hac"kle\, v. t. [imp. & p. p. Hackled (h[a^]k"k'ld);
   p. pr. & vb. n. Hackling (h[a^]k"kl[i^]ng).]
   1. To separate, as the coarse part of flax or hemp from the
      fine, by drawing it through the teeth of a hackle or
      hatchel.
      [1913 Webster]

   2. To tear asunder; to break in pieces.
      [1913 Webster]

            The other divisions of the kingdom being hackled and
            torn to pieces.                       --Burke.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hatchel \Hatch"el\ (-[e^]l; 277), n. [OE. hechele, hekele; akin
   to D. hekel, G. hechel, Dan. hegle, Sw. h[aum]kla, and prob.
   to E. hook. See Hook, and cf. Hackle, Heckle.]
   An instrument with long iron teeth set in a board, for
   cleansing flax or hemp from the tow, hards, or coarse part; a
   kind of large comb; -- called also hackle and heckle.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hackle
    n 1: long slender feather on the necks of e.g. turkeys and
         pheasants
    v 1: comb with a heckle; "heckle hemp or flax" [syn: heckle,
         hackle, hatchel]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "hackle":
   card, comb, covert, crest, curry, feather, feathers, hack, haggle,
   hatchel, heckle, mail, panache, pinion, plumage, plume, plumule,
   quill, rake, scapular, slash, speculum, topknot, tuft