callouses

noun

1. 1.A hardened area of the skin (especially on the foot or hand) caused by repeated friction, wear or use.
2. 2.The material of repair in fractures of bone; a substance exuded at the site of fracture, which is at first soft or cartilaginous in consistency, but is ultimately converted into true bone and unites the fragments into a single piece.
3. 3.The new formation over the end of a cutting, before it puts out rootlets.
4. 4.A shining area on the frons of many species of Tabanomorpha (horse flies and relatives).