The Collaborative International Dictionary of English v.0.48:

callousness \cal"lous*ness\ n.
   lack of passion or feeling.

   Syn: unfeelingness, hardness, insensibility.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

callousness
    n 1: devoid of passion or feeling; hardheartedness [syn:
         unfeelingness, callousness, callosity, hardness,
         insensibility]