[{"Bold_text": "adjective", "List Items": ["utterly unyielding in attitude or opinion in spite of all appeals, urgings, etc.Synonyms: uncompromising , rigid , inflexible Antonyms: yielding , easygoing , flexible", "too hard to cut, break, or pierce."]}, {"Bold_text": "noun", "List Items": ["any impenetrably or unyieldingly hard substance.", "a legendary stone of impenetrable hardness, formerly sometimes identified with the diamond."]}]