Webster's Revised Unabridged Dictionary · 1913

Obdurate

Obdurate , adjective

[Latin obduratus, past participle of obdurare to harden; ob (see Ob-)+ durare to harden, durus hard. See Dure.]

1.
Hardened in feelings, esp. against moral or mollifying influences; unyielding; hard-hearted; stubbornly wicked.
The very custom of evil makes the heart obdurate against whatsoever instructions to the contrary. — Hooker
Art thou obdurate, flinty, hard as steel, Nay, more than flint, for stone at rain relenteth? — Shakespeare
2.
Hard; harsh; rugged; rough; intractable.
Obdurate consonants. — Swift
There is no flesh in man's obdurate heart. — Cowper

Sometimes accented on the second syllable, especially by the older poets.

Obdurate , transitive verb

To harden. [Obsolete]