callus (Noun) — An area of skin that is thick or hard from continual pressure or friction (as the sole of the foot).
callus (Noun) — Bony tissue formed during the healing of a fractured bone.
callus (Noun) — (botany) an isolated thickening of tissue, especially a stiff protuberance on the lip of an orchid.
callus (Verb) — Cause a callus to form on. ex. "The long march had callused his feet"
callus (Verb) — Form a callus or calluses. ex. "His foot callused"