The Collaborative International Dictionary of English v.0.48:

Cracksman \Cracks"man\ (kr?ks"man), n., pl. Cracksmen (-men).
   A burglar. [Slang]
   [1913 Webster]

WordNet (r) 3.0 (2006):

cracksman
    n 1: a thief who breaks open safes to steal valuable contents
         [syn: safebreaker, safecracker, cracksman]