The Collaborative International Dictionary of English v.0.48:

menu \men"u\ (m[e^]n"y[=oo]), n. [F., slender, thin, minute. See
   4th Minute.]
   1. The details of a banquet; a list of the dishes served at a
      meal, whether or not one has a choice.
      [PJC]

   2. Any list of objects, activities, etc. from which to
      choose; a selection of alternatives.
      [PJC]

   3. Hence:A list of dishes form which to choose at a
      restaurant; a bill of fare.
      [1913 Webster]

   4. Hence: (Computers) A list displayed on the computer
      screen, by which a program provides the user with
      different options for processing by the program. It
      usually includes a mechanism, such as pointing by a mouse
      or selection by arrow keys, to select the desired option
      from those on the list. Depending on how the menu is
      displayed, it may be a pop-up menu or pull-down menu.
      [PJC]

The Free On-line Dictionary of Computing (30 December 2018):

pull-down menu
drop-down menu
pop-down menu

    (Or "drop-down menu", "pop-down menu") A
   menu in a graphical user interface, whose title is
   normally visible but whose contents are revealed only when the
   user activates it, normally by pressing the mouse button
   while the pointer is over the title, whereupon the menu
   items appear below the title.  The user may then select an
   item from the menu or click elsewhere, in either case the menu
   contents are hidden again.  A menu item is selected either by
   dragging the mouse from the menu title to the item and
   releasing or by clicking the title and then the item.

   When a pull-down menu appears in the main area of a window, as
   opposed to the menu bar, it may have a small,
   downward-pointing triangle to the right.

   Compare: scrollable list.

   (1999-09-22)