OBSTINATE

[adjective] - unreasonably determined, esp. to act in a particular way and not to change at all, despite argument or persuasion; stubbornThe bank is being obstinate about my overdraft - they're refusing to let me have more than £500 this time.He has an obstinate belief in his own ability.An obstinate problem, situation or thing is one that is difficult to deal with, remove or defeat.obstinate weedsThere is some obstinate dry rot in the floor of our house.Invading troops met with obstinate resistance by guerilla forces.