obstinacy

Concise Oxford English Dictionary © 2008 Oxford University Press:
obstinate/ˈɒbstɪnət/

▶adjective

• 1 stubbornly refusing to change one's opinion or chosen course of action.

• 2 difficult to overcome or change: an obstinate problem.

– derivatives
obstinacy noun,
obstinately adverb.

– origin ME: from L. obstinatus, obstinare ‘persist’.