ad•a•mantPronunciation: (ad'u-munt, -mant"), [key]
utterly unyielding in attitude or opinion in spite of all appeals, urgings, etc.
too hard to cut, break, or pierce.
any impenetrably or unyieldingly hard substance.
a legendary stone of impenetrable hardness, formerly sometimes identified with the diamond.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.