Source : Webster's Revised Unabridged Dictionary (1913)

Shackle \Shac"kle\, n.
   Stubble. [Prov. Eng.] --Pegge.

Shackle \Shac"kle\, v. t. [imp. & p. p. {Shackled}; p. pr. & vb.
   n. {Shackling}.]
   1. To tie or confine the limbs of, so as to prevent free
      motion; to bind with shackles; to fetter; to chain.

            To lead him shackled, and exposed to scorn Of
            gathering crowds, the Britons' boasted chief. --J.
                                                  Philips.

   2. Figuratively: To bind or confine so as to prevent or
      embarrass action; to impede; to cumber.

            Shackled by her devotion to the king, she seldom
            could pursue that object.             --Walpole.

   3. To join by a link or chain, as railroad cars. [U. S.]

   {Shackle bar}, the coupling between a locomotive and its
      tender. [U.S.]

   {Shackle bolt}, a shackle. --Sir W. Scott.

Shackle \Shac"kle\, n. [Generally used in the plural.] [OE.
   schakkyll, schakle, AS. scacul, sceacul, a shackle, fr.
   scacan to shake; cf. D. schakel a link of a chain, a mesh,
   Icel. sk["o]kull the pole of a cart. See {Shake}.]
   1. Something which confines the legs or arms so as to prevent
      their free motion; specifically, a ring or band inclosing
      the ankle or wrist, and fastened to a similar shackle on
      the other leg or arm, or to something else, by a chain or
      a strap; a gyve; a fetter.

            His shackles empty left; himself escaped clean.
                                                  --Spenser.

   2. Hence, that which checks or prevents free action.

            His very will seems to be in bonds and shackles.
                                                  --South.

   3. A fetterlike band worn as an ornament.

            Most of the men and women . . . had all earrings
            made of gold, and gold shackles about their legs and
            arms.                                 --Dampier.

   4. A link or loop, as in a chain, fitted with a movable bolt,
      so that the parts can be separated, or the loop removed; a
      clevis.

   5. A link for connecting railroad cars; -- called also
      {drawlink}, {draglink}, etc.

   6. The hinged and curved bar of a padlock, by which it is
      hung to the staple. --Knight.

   {Shackle joint} (Anat.), a joint formed by a bony ring
      passing through a hole in a bone, as at the bases of
      spines in some fishes.

Source : WordNet®

shackle
     n 1: a restraint that confines or restricts freedom (especially
          something used to tie down or restrain a prisoner) [syn:
           {bond}, {hamper}, {trammel}, {trammels}]
     2: a U-shaped bar; the open end can be passed through chain
        links and closed with a bar
     v 1: bind the arms of [syn: {pinion}]
     2: restrain with fetters [syn: {fetter}]