What does "callous" mean?

Callous: Hardened in mind; insensible; unfeeling; unsusceptible. "The callous diplomatist." Macaulay. It is an immense blessing to be perfectly callous to ridicule. T. Arnold. See Obdurate. -- Cal"lous*ly, adv. -- Cal"lous*ness, n. A callousness and numbness of soul. Bentley.

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