thor·ough·pin
(thûr′ō-pĭn′, thûr′ə-, thŭr′-)n. 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.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
thoroughpin
(ˈθʌrəˌpɪn) n (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]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
thor•ough•pin
(ˈθɜr əˌpɪn, ˈθʌr-)
n. an abnormal swelling just above the hock of a horse.
[1780–90]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.