Also found in: Medical.
thor·ough·pin(thûr′ō-pĭn′, thûr′ə-, thŭr′-)
An abnormal swelling on either side of the hock joint of horses and related animals.
[From its resemblance to a pin passing through the hock.]
(Veterinary Science) an inflammation and swelling on both sides of the hock joint of a horse affecting the sheath of the deep flexor tendon
[C18: so called because it makes the leg look as if it has a pin stuck through it]
thor•ough•pin(ˈθɜr əˌpɪn, ˈθʌr-)
an abnormal swelling just above the hock of a horse.