adamant
Cross references: 1. inflexible 1. ad.a.mant \'ad-*-m*nt, -.mant\ n [ME, fr. OF, fr. L adamant-, adamas hardest metal, diamond fr. Gk] 1: a stone believed to be of impenetrable hardness 2: an unbreakable or extremely hard substance 2. adamant aj : unshakable or immovable esp. in opposition : UNYIELDING - ad.a.mant.ly av