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

context-sensitive menu

    A menu which appears in response to a
   user action (typically a mouse click) and whose contents are
   determined by which application window was clicked or has
   the input focus.

   Most GUIs use a secondary mouse button (right or middle) to
   call up a context-sensitive menu as the primary mouse button
   is normally used to interact with objects which are already
   visible.

   The context-sensitive menu often contains functions that are
   also available in a menu bar but the context-sensitive menu
   provides quick access to a subset of functions that are
   particularly relevant to the window area clicked on.

   The RISC OS WIMP uses only context-sensitive menus (always
   invoked using the middle mouse button).  This saves screen
   space and reduces mouse movement compared to a menu bar.

   (1999-09-22)