I. ˈka-ləs noun
Etymology: Latin
Date: 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 healing
3. : soft tissue that forms over a wounded or cut plant surface
II. verb
Date: 1864
intransitive verb
: to form callus
transitive verb
: to cause callus to form on