Source : Webster's Revised Unabridged Dictionary (1913)

Thick-skinned \Thick"-skinned`\, a.
   Having a thick skin; hence, not sensitive; dull; obtuse.
   --Holland.

Source : WordNet®

thick-skinned
     adj : emotionally hardened; "a callous indifference to suffering";
           "cold-blooded and indurate to public opinion" [syn: {callous},
            {indurate}, {pachydermatous}]