All 3 Uses

callous
in
Brideshead Revisited
(Auto-generated)

I simply don't understand how anyone can be so callously wicked.†
p. 193.9
'Callously wicked,' wantonly cruel.'†
p. 198.9 *
It was characteristic of an old, atavistic callousness that went with her delicacy that, even at this crisis, she did not think it unreasonable to put Sebastian in Rex's charge on the journey to Dr. Borethus, and Rex, having failed her in that matter, went on to Monte Carlo, where he completed her rout.†
p. 217.9

callousness = insensitivity (emotionally)

Definitions:

(1) (callous as in: callous indifference)
heartless (cruel lack of concern for other's feelings)
(2) (callous as in: a thick callous)
thickened skin that comes from rubbing as when having calluses on the hands from doing much work with a shovel
(3) (meaning too rare to warrant focus)