persistent

adjective

• 1continuing firmly or obstinately in a course of action in spite of difficulty or opposition:one of the government’s most persistent critics

• 2continuing to exist or endure over a prolonged period:persistent rain will affect many areas persistent reports of human rights abuses by the military
• (of a chemical or radioactivity) remaining within the environment for a long time after its introduction:PCBs are persistent environmental contaminants

• 3 Botany & Zoology (of a part of an animal or plant, such as a horn, leaf, etc.) remaining attached instead of falling off in the normal manner.