callous

This term describes a hardened state, whether physical or emotional. When applied to skin, it refers to the biological process of thickening to protect against abrasion, creating a literal barrier between the body and external friction.

In a psychological sense, it describes a similar emotional hardening. It suggests a deliberate or habitual lack of empathy, where a person has become impervious to the pain of others. This connotation is strongly negative, implying a coldness that is not merely accidental but a characteristic trait of the individual's personality.