The term 'more obdurate' can be defined as being more stubborn or unyielding. The two crossword solutions for this term are 'flintier' (8 letters) and 'stonier' (7 letters). Both words refer to something that is hard, unyielding, and difficult to change. Flintier is derived from the mineral flint, which is a type of hard, sedimentary rock, while stonier is derived from the word stone, which is another type of hard, sedimentary rock. Both words imply that something is very difficult to change or alter.