The Collaborative International Dictionary of English v.0.48:
Shackle \Shac"kle\, v. t. [imp. & p. p. Shackled; p. pr. & vb.
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.
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
Shackle bolt, a shackle. --Sir W. Scott.