The Collaborative International Dictionary of English v.0.48:

Casehardened \Case"hard`ened\, a.
   1. Having the surface hardened, as iron tools.
      [1913 Webster]

   2. Hardened against, or insusceptible to, good influences;
      rendered callous by persistence in wrongdoing or
      resistance of good influences; -- said of persons.
      [1913 Webster]

WordNet (r) 3.0 (2006):

case-hardened
    adj 1: used of persons; emotionally hardened; "faced a case-
           hardened judge" [syn: case-hardened, hardened, hard-
           boiled]