A shackle is a metal ring that can be locked around someone's wrist or ankle, usually to keep them from moving.
Shackles are often thought of as being used to hold someone prisoner or to stop them from running away.
Examples:
The prisoner's shackles clanked as he walked.
The pirate put shackles on the captured sailors.
She couldn't run because of the heavy shackles on her feet.
The shackles were too big for the little dog!
The giant wore shackles made of iron.
The shackles were cold and heavy on his wrists.
To shackle someone means to put shackles on them, to hold them prisoner, or to stop them from moving freely.
When you shackle someone, it usually means you are taking away their freedom or stopping them from doing something they want to do.
Examples:
The guards shackled the prisoner before taking him to his cell.
They shackled the criminal to keep him from escaping.
She shackled her bike to the post so no one would steal it.
I'm going to shackle you to this chair so you can't run away!
The evil villain shackled the hero and left him to die.
Don't shackle me, I promise I won't run away!