'Splint bone' definitions:

Definition of 'splint bone'

noun

A rudimentary metacarpal or metatarsal bone on either side of the cannon bone in the leg of a horse or related animal

From: GCIDE

Splint \Splint\, n. [Akin to D. splinter,G. splinter, splitter, Dan. splint, Sw. splint a kind of spike, a forelock (in nautical use), Sw. splintato splint, splinter, Dan. splinte, and E. split. See Split, v. t., and cf. Splent.]
1. A piece split off; a splinter. [1913 Webster]
2. (Surg.) A thin piece of wood, or other substance, used to keep in place, or protect, an injured part, especially a broken bone when set. [1913 Webster]
3. (Anat.) A splint bone. [1913 Webster]
4. (Far.) A disease affecting the splint bones, as a callosity or hard excrescence. [1913 Webster]
5. (Anc. Armor.) One of the small plates of metal used in making splint armor. See Splint armor, below. [1913 Webster]
The knees and feet were defended by splints, or thin plates of steel. --Sir. W. Scott. [1913 Webster]
6. Splint, or splent, coal. See Splent coal, under Splent. [1913 Webster]
Splint armor,a kind of ancient armor formed of thin plates of metal, usually overlapping each other and allowing the limbs to move freely.
Splint bone (Anat.), one of the rudimentary, splintlike metacarpal or metatarsal bones on either side of the cannon bone in the limbs of the horse and allied animals.
Splint coal. See Splent coal, under Splent. [1913 Webster]