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