callus

1. A hardened area of the skin (especially on the foot or hand) caused by repeated friction, wear or use. (countable, uncountable)
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. (countable, uncountable)
3. The new formation over the end of a cutting, before it puts out rootlets. (countable, uncountable)
4. In orchids, a fleshy outgrowth from the labellum. (countable, uncountable)
5. In grasses, a hardened extension from the base of a floret, which may or may not elongate and is often covered in hairs or bristles. (countable, uncountable)
6. A shining area on the frons of many species of Tabanomorpha (horse flies and relatives). (countable, uncountable)

Plural calluses