pertinacious
ETYM Latin pertinax, -acis; per + tenax tenacious. Related to Per-, and Tenacious.
1. Holding or adhering to any opinion, purpose, or design, with obstinacy; perversely persistent; obstinate.
2. Resolute; persevering; constant; steady.
dogged · dour · obstinate · stubborn · tenacious · unregenerate · unyielding
Perthes' incision · Perthes' test · per thousand · Perthshire · Pertik's diverticulum · pertinacious · pertinaciously · pertinaciousness · pertinacity · pertinence · pertinency