[ad.a.mant] n [ME, fr. MF, fr. L adamant-, adamas hardest metal, diamond, fr. Gk] (14c) 1: a stone (as a diamond) formerly believed to be of impenetrable hardness
2: an unbreakable or extremely hard substance
[2]adamant adj (1923): unshakable or immovable esp. in opposition: unyielding syn see inflexible -- ad.a.mant.ly adv