retractable       
adjective  formal uk/rɪˈtræk.tə.bəl/ us/rɪˈtræk.tə.bəl/
 可缩回的;可收起的
that can be pulled back or in
  Cats have retractable claws. 猫的爪子可以伸缩。 
 The house has a swimming pool with a retractable roof. 这栋房子有一个带可伸缩屋顶的游泳池。 
 See: retract
 - More examples
 - a retractable needle/syringe
 - The pool is equipped with a fully retractable safety cover.
 - Many major new stadiums around the world have retractable seating so they can accommodate athletics.