persistent          
adjective uk/pəˈsɪs.tənt/ us/pɚˈsɪs.tənt/
 持续的;存留的;顽强存在的
lasting for a long time or difficult to get rid of
  a persistent smell/skin rash 持续不散的气味/顽固的皮疹 
 Symptoms of the illness include a high temperature and a persistent dry cough. 病症包括高烧和持久的干咳。 
 There have been persistent rumours that the principal might take early retirement. 不断有谣言说校长可能会提前退休。 
 C2 坚持不懈的;执意的
Someone who is persistent continues doing something or tries to do something in a determined but often unreasonable way.
  Be persistent - don't give up. 要坚持不懈——别放弃。 
 He has been a persistent critic of the president. 他一贯对总统持批评态度。 
 She is a persistent offender and has been arrested five times this year for shoplifting. 她是个惯犯,今年已5次因在商店行窃被捕。