[cal.lus] n [L] (1563) 1: a thickening of or a hard thickened area on skin or bark
2: a mass of exudate and connective tissue that forms around a break in a bone and is converted into bone in the healing of the break
3: soft tissue that forms over a wounded or cut plant surface
[2]callus vi (1864): to form callus ~ vt: to cause callus to form on