drop-down
/ˈdrɒpdaʊn/adjective
attrib.
1- dropping down or unfolding when required可折叠的; 可展开的：
a drop-down bed.
一张折叠床。
1.1
- Computing (of a menu) appearing below a menu title when it is selected, and remaining until used or dismissed【计算机】（菜单）下拉式的。比较PULL-DOWN.