pertinacious

obstinate, dogged, stubborn, pertinacious, mulish mean fixed and unyielding in course or purpose. obstinate implies usually an unreasonable persistence <an obstinate proponent of conspiracy theories>. dogged suggests an admirable often tenacious and unwavering persistence <pursued the story with dogged perseverance>. stubborn implies sturdiness in resisting change which may or may not be admirable <a person too stubborn to admit error>. pertinacious suggests an annoying or irksome persistence <a pertinacious salesclerk refusing to take no for an answer>. mulish implies a thoroughly unreasonable obstinacy <a mulish determination to have his own way>.