[ keys-hahr-dn ]
/ ˈkeɪsˌhɑr dn /

verb (used with object)

Metallurgy. to make the outside surface of (an alloy having an iron base) hard by carburizing and heat treatment, leaving the interior tough and ductile.
to harden in spirit so as to render insensible or insensitive to external impressions or influences; make callous.

Origin of caseharden

First recorded in 1670–80; case2 + harden Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for caseharden