1. (v. t.) To subject to great heat, and then cool slowly, as glass, cast iron, steel, or other metal, for the purpose of rendering it less brittle; to temper; to toughen.

2. (v. t.) To heat, as glass, tiles, or earthenware, in order to fix the colors laid on them.

Philistine anneal apathetic asleep backed benumbed brazen brutalize calcified calcify calloused case harden case-hardened cold cold of heart coldblooded coldhearted conscienceless cornify crusted crusty crystallized dead deadened dull firm flinthearted flinty fossilize fossilized granulated hard hard of heart hard-boiled hard-nosed harden hardened hardhearted heartless hornified impassible impenitent imperceptive impercipient impervious incrusted indifferent indurate indurated insensate insensible insensitive insentient insolent inure inured lapidified lapidify lithify lost to shame numb numbed obdurate obtuse ossified ossify pachydermatous petrified petrify proof against reinforced rigidified sclerotic seared set shameless solidified steel steeled steeled against steely stiffened stony stonyhearted strengthened temper thick-skinned thick-witted tough toughen toughened unabject unblushing uncaring uncompassionate uncontrite unemotional unfeeling unfelt unmelted unmerciful unnatural unperceptive unrepentant unrepenting unresponsive unsoftened unsympathetic untouched vitrified vitrify