If you describe someone as ~, you mean that they have had so much experience of something bad or unpleasant that they are no longer affected by it in the way that other people would be.
...~ criminals.
...~ politicians.
ADJ: usu ADJ n
HARDENED
Meaning of HARDENED in English
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012