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. [1913 Webster]
"His shackles empty left; himself escaped clean." [1913 Webster]

2.  Hence, that which checks or prevents free action. [1913 Webster]
"His very will seems to be in bonds and shackles." [1913 Webster]

3.  A fetterlike band worn as an ornament. [1913 Webster]
"Most of the men and women . . . had all earrings made of gold, and gold shackles about their legs and arms." [1913 Webster]

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. [1913 Webster]

5.  A link for connecting railroad cars; -- called also drawlink, draglink, etc. [1913 Webster]

6.  The hinged and curved bar of a padlock, by which it is hung to the staple. Knight. [1913 Webster]

1.  To tie or confine the limbs of, so as to prevent free motion; to bind with shackles; to fetter; to chain. [1913 Webster]
"To lead him shackled, and exposed to scorn
Of gathering crowds, the Britons' boasted chief." [1913 Webster]

2.  Figuratively: To bind or confine so as to prevent or embarrass action; to impede; to cumber. [1913 Webster]
"Shackled by her devotion to the king, she seldom could pursue that object." [1913 Webster]

3.  To join by a link or chain, as railroad cars. [1913 Webster]

shackle, n. & v.
--n.
1 a metal loop or link, closed by a bolt, to connect chains etc.
2 a fetter enclosing the ankle or wrist.
3 (usu. in pl.) a restraint or impediment.
--v.tr. fetter, impede, restrain.

Idiom:
shackle-bolt
1 a bolt for closing a shackle.
2 a bolt with a shackle at its end.

Etymology:
OE sc(e)acul fetter, corresp. to LG sh{auml}kel link, coupling, ON sk{ouml}kull wagon-pole f. Gmc

N  connection, vinculum, link, connective, connection, junction, bond of union, copula, hyphen, intermedium, bracket, bridge, stepping-stone, isthmus, bond, tendon, tendril, fiber, cord, cordage, riband, ribbon, rope, guy, cable, line, halser, hawser, painter, moorings, wire, chain, string, fastener, fastening, tie, ligament, ligature, strap, tackle, rigging, standing rigging, running rigging, traces, harness, yoke, band ribband, bandage, brace, roller, fillet, inkle, with, withe, withy, thong, braid, girder, tiebeam, girth, girdle, cestus, garter, halter, noose, lasso, surcingle, knot, running knot, cabestro, cinch, lariat, legadero, oxreim, suspenders, pin, corking pin, nail, brad, tack, skewer, staple, corrugated fastener, clamp, U-clamp, C-clamp, cramp, cramp iron, ratchet, detent, larigo, pawl, terret, treenail, screw, button, buckle, clasp, hasp, hinge, hank, catch, latch, bolt, latchet, tag, tooth, hook, hook and eye, lock, holdfast, padlock, rivet, anchor, grappling iron, trennel, stake, post, cement, glue, gum, paste, size, wafer, solder, lute, putty, birdlime, mortar, stucco, plaster, grout, viscum, shackle, rein, prop.

VB  hinder, impede, filibuster, impedite, embarrass, keep off, stave off, ward off, obviate, avert, antevert, turn aside, draw off, prevent, forefend, nip in the bud, retard, slacken, check, let, counteract, countercheck, preclude, debar, foreclose, estop, inhibit, shackle, restrict, obstruct, stop, stay, bar, bolt, lock, block, block up, choke off, belay, barricade, block the way, bar the way, stop the way, forelay, dam up, put on the brake, scotch the wheel, lock the wheel, put a spoke in the wheel, put a stop to, traverse, contravene, interrupt, intercept, oppose, hedge in, hedge round, cut off, inerclude, interpose, interfere, intermeddle, cramp, hamper, clog, clog the wheels, cumber, encumber, incumber, handicap, choke, saddle with, load with, overload, lay, lumber, trammel, tie one's hands, put to inconvenience, incommode, discommode, discompose, hustle, corner, drive into a corner, run foul of, fall foul of, cross the path of, break in upon, thwart, frustrate, disconcert, balk, foil, faze, feaze, feeze, baffle, snub, override, circumvent, defeat, spike guns, spoil, mar, clip the wings of, cripple, put an extinguisher on, damp, dishearten, discountenance, throw cold water on, spoil sport, lay a wet blanket, throw a wet blanket on, cut the ground from under one, take the wind out of one's sails, undermine, be in the way of, stand in the way of, act as a drag, hang like a millstone round one's neck.

VB  restrain, check, put under restraint, lay under restraint, enthral, enthrall, inthral, inthrall, bethral, bethrall, restrict, debar, constrain, coerce, curb, control, hold back, hold from, hold in, hold in check, hold within bounds, keep back, keep from, keep in, keep in check, keep within bounds, hold in leash, hold in leading strings, withhold, keep under, repress, suppress, smother, pull in, rein in, hold, hold fast, keep a tight hand on, prohibit, inhibit, cohibit, enchain, fasten, fetter, shackle, entrammel, bridle, muzzle, hopple, gag, pinion, manacle, handcuff, tie one's hands, hobble, bind hand and foot, swathe, swaddle, pin down, tether, picket, tie down, tie up, secure, forge fetters, disable, hamstring (incapacitate), confine, shut up, shut in, clap up, lock up, box up, mew up, bottle up, cork up, seal up, button up, hem in, bolt in, wall in, rail in, impound, pen, coop, inclose, cage, incage, encage, close the door upon, cloister, imprison, immure, incarcerate, entomb, clap under hatches, lay under hatches, put in irons, put in a strait-waistcoat, throw into prison, cast into prison, put into bilboes, arrest, take up, take charge of, take into custody, take prisoner, take captive, make prisoner, make captive, captivate, lead captive, lead into captivity, send to prison, commit to prison, commit, give in charge, give in custody, subjugate.

N  prison, prison house, jail, gaol, cage, coop, den, cell, stronghold, fortress, keep, donjon, dungeon, Bastille, oubliette, bridewell, house of correction, hulks, tollbooth, panopticon, penitentiary, guardroom, lockup, hold, round house, watch house, station house, sponging house, station, house of detention, black hole, pen, fold, pound, inclosure, isolation (exclusion), penal settlement, penal colony, bilboes, stocks, limbo, quod, calaboose, chauki, choky, thana, workhouse, Newgate, Fleet, Marshalsea, King's Bench, Queen's Bench, bond, bandage, irons, pinion, gyve, fetter, shackle, trammel, manacle, handcuff, straight jacket, strait jacket, strait-jacket, strait-waistcoat, hopples, vice, vise, yoke, collar, halter, harness, muzzle, gag, bit, brake, curb, snaffle, bridle, rein, reins, bearing rein, martingale, leading string, tether, picket, band, guy, chain, cord, cavesson, hackamore, headstall, jaquima, lines, ribbons, bolt, deadbolt, bar, lock, police lock, combination lock, padlock, rail, wall, stone wall, paling, palisade, fence, picket fence, barbed wire fence, Cyclone fence, stockade fence, chain-link fence, barrier, barricade, drag.