I. ˈka-ləs adjective
Etymology: Middle English, from Latin callosus, from callum, callus callous skin
Date: 15th century
1.
a. : being hardened and thickened
b. : having calluses
callous hands
2.
a. : feeling no emotion
b. : feeling or showing no sympathy for others : hard-hearted
a callous indifference to suffering
• cal·lous·ly adverb
• cal·lous·ness noun
II. transitive verb
Date: 1834
: to make callous
hands callous ed by hard manual labor