pertinacious
/ˌpɜːrtnˈeɪʃəs/
adjective
- Holding firmly to an opinion, purpose, or course of action; stubbornly persistent.
- Despite many failures, his pertinacious spirit never wavered.
- Her pertinacious efforts to learn the piano finally paid off.
- The pertinacious reporter kept asking questions until she got an answer.