Definition of "fetlock"

fetlock

noun
plural fetlocks
1. A joint of the horse's leg below the knee or hock and above the hoof.
  Quotations
  It was the better part of a mile wide, but save for some fathoms in the middle, where the Sker current ran, it was no deeper even at flood than a horse's fetlocks.
  1902, John Buchan, The Outgoing of the Tide
2. The tuft of hair that grows at this joint.