drop-down menu
noun /ˌdrɒp daʊn ˈmenjuː/
  /ˌdrɑːp daʊn ˈmenjuː/
 (also drop-down, drop-down list)
 (computing)- a menu that appears on a computer screen when you choose it, and that stays there until you choose one of the functions on itTopics Computersc1