Adjective: case-hardened keys haa(r)-d(u)nd
- Used of persons; emotionally hardened
"faced a case-hardened judge";
- hardened, hard-boiled
- Harden the surface of iron or steel by infusing carbon into the surface layer
"They casehardened the gears to improve wear resistance"
- Render (a person) insensitive to hardship or criticism
"The harsh training casehardened the recruits"
See also: hard
Encyclopedia: Case-hardened