Source : Webster's Revised Unabridged Dictionary (1913)

Adamant \Ad"a*mant\ ([a^]d"[.a]*m[a^]nt), n. [OE. adamaunt,
   adamant, diamond, magnet, OF. adamant, L. adamas, adamantis,
   the hardest metal, fr. Gr. 'ada`mas, -antos; 'a priv. +
   dama^,n to tame, subdue. In OE., from confusion with L.
   adamare to love, be attached to, the word meant also magnet,
   as in OF. and LL. See {Diamond}, {Tame}.]
   1. A stone imagined by some to be of impenetrable hardness; a
      name given to the diamond and other substances of extreme
      hardness; but in modern mineralogy it has no technical
      signification. It is now a rhetorical or poetical name for
      the embodiment of impenetrable hardness.

            Opposed the rocky orb Of tenfold adamant, his ample
            shield.                               --Milton.

   2. Lodestone; magnet. [Obs.] ``A great adamant of
      acquaintance.'' --Bacon.

            As true to thee as steel to adamant.  --Greene.

Source : WordNet®

adamant
     adj : not capable of being swayed or diverted from a course;
           unsusceptible to persuasion; "he is adamant in his
           refusal to change his mind"; "Cynthia was inexorable;
           she would have none of him"- W.Churchill; "an
           intransigent conservative opposed to every liberal
           tendancy" [syn: {adamantine}, {inexorable}, {intransigent}]

adamant
     n : very hard native crystalline carbon valued as a gem [syn: {diamond}]