pertinacious

Holding tenaciously to an opinion or purpose.

When that divine took his leave, not a little discomfited and amazed at the pertinacious obstinacy of the women, Laura repeated her embraces and arguments with tenfold fervour to Helen, who felt that there was a great deal of cogency in most of the latter.

He would really have to make up his mind to care for his wife or not to care for her. What would Lady Vandeleur say to one alternative, and what would little Joscelind say to the other? That is what it was to have a pertinacious father and to be an accommodating son.

Stubbornly resolute or tenacious.

[O]ne of the Dissenters, which I could, but forbear, to name appeared to Dr. Sanderson to be so bold, so troublesome, and so illogical in the dispute, as forced patient Dr. Sanderson, who was then Bishop of Lincoln, and a moderator with other Bishops, to say, with an unusual earnestness, "That he had never met with a man of more pertinacious confidence, and less abilities, in all his conversation."