cannon bone

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A supporting bone of the leg in some hoofed mammals, analogous to the metacarpus of the hand or the metatarsus of the foot in humans.

from The Century Dictionary.

• noun In farriery and vet, surg., one of the functional and complete metacarpal or metatarsal bones of a hoofed quadruped, supporting the weight of the body upon the feet.

from the GNU version of the Collaborative International Dictionary of English.

• (Anat.) See Canon Bone.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A bone resulting from the fusion of metacarpals or metatarsals in some artiodactyls.
• noun The metacarpal of a horse.
• noun The metatarsal of a horse.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun greatly developed metatarsal or metacarpal bone in the shank or cannon part of the leg in hoofed mammals