Merriam-Webster Collegiate Dictionary - indurate

 I. adjective  Date: 14th century physically or morally hardened  II. verb  (-rated; -rating)  Etymology: Latin induratus, past participle of indurare, from in- + durare to harden, from durus hard — more at during  Date: 1538  transitive verb  1. to make unfeeling, stubborn, or obdurate  2. to make hardy ; inure  3. to make hard great heat ~s clay  4. to establish firmly ; confirm  intransitive verb  1. to grow hard ; harden  2. to become established