How could we have been so callous as to doubt her testimony?
The implication, of course, was that Khadr was, in the words of one interrogator, “cold and callous.”
Romney lost in part because he allowed his campaign and personality to be defined as extreme and callous.
c.1400, "hardened," in the physical sense, from Latin callosus "thick-skinned," from callus, callum "hard skin" (see callus). The figurative sense of "unfeeling" appeared in English by 1670s. Related: Callously; callousness.
callous cal·lous (kāl'əs)
Of, relating to, or characteristic of a callus or callosity.