1. Having calluses; toughened: callous skin on the elbow.
2. Emotionally hardened; unfeeling: a callous indifference to the suffering of others.
tr. & intr.v. cal·loused, cal·lous·ing, cal·lous·es
To make or become callous.
[Middle English, from Old French cailleux, from Latin callōsus, from callum, hard skin.]
Usage Note: Do not confuse the adjective callous, as in Years of dealing with criminals had left her callous, with the noun callus, as in I have a callus on my thumb. Also, do not confuse the verb callous, which means "to make or become callous," with the verb callus "to form or develop hardened tissue."
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.