verb
Etymology: case (II) (covering) + harden
transitive verb
1. : to harden (a ferrous alloy) so that the surface layer is made considerably harder than the interior (as by carburizing and quenching, cyaniding, carbonitriding, or nitriding)
2. : to make callous or insensible
3.
a. : to harden superficially, producing a hard, durable, or inflexible surface ; specifically : to affect (lumber) with case hardening
b. : to temper (glass)
intransitive verb
: to become affected by the process of case hardening