The Collaborative International Dictionary of English v.0.48:

Obdurate \Ob"du*rate\, a. [L. obduratus, p. p. 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.
      [1913 Webster]

            The very custom of evil makes the heart obdurate
            against whatsoever instructions to the contrary.
                                                  --Hooker.
      [1913 Webster]

            Art thou obdurate, flinty, hard as steel,
            Nay, more than flint, for stone at rain relenteth?
                                                  --Shak.
      [1913 Webster]

   2. Hard; harsh; rugged; rough; intractable. "Obdurate
      consonants." --Swift.
      [1913 Webster]

   Note: Sometimes accented on the second syllable, especially
         by the older poets.
         [1913 Webster]

               There is no flesh in man's obdurate heart.
                                                  --Cowper.
         [1913 Webster]

   Syn: Hard; firm; unbending; inflexible; unyielding; stubborn;
        obstinate; impenitent; callous; unfeeling; insensible;
        unsusceptible.

   Usage: Obdurate, Callous, Hardened. Callous denotes a
          deadening of the sensibilities; as, a callous
          conscience. Hardened implies a general and settled
          disregard for the claims of interest, duty, and
          sympathy; as, hardened in vice. Obdurate implies an
          active resistance of the heart and will aganst the
          pleadings of compassion and humanity.
          [1913 Webster] -- Ob"du*rate*ly, adv. --
          Ob"du*rate*ness, n.
          [1913 Webster]

WordNet (r) 3.0 (2006):

obdurately
    adv 1: in a stubborn unregenerate manner; "she remained
           stubbornly in the same position" [syn: stubbornly,
           pig-headedly, obdurately, mulishly, obstinately,
           cussedly]