WordNet (r) 3.0 (2006):

GUI
    n 1: a user interface based on graphics (icons and pictures and
         menus) instead of text; uses a mouse as well as a keyboard
         as an input device [syn: graphical user interface, GUI]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

GUI
       Graphical User Interface (UI)


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

Graphical User Interface
GUI

    (GUI) The use of pictures rather than just
   words to represent the input and output of a program.  A
   program with a GUI runs under some windowing system
   (e.g. The X Window System, MacOS, Microsoft Windows,
   Acorn RISC OS, NEXTSTEP).  The program displays certain
   icons, buttons, dialogue boxes, etc. in its windows on
   the screen and the user controls it mainly by moving a
   pointer on the screen (typically controlled by a mouse)
   and selecting certain objects by pressing buttons on the mouse
   while the pointer is pointing at them.  This contrasts with a
   command line interface where communication is by exchange of
   strings of text.

   Windowing systems started with the first real-time graphic
   display systems for computers, namely the SAGE Project
   [Dates?] and Ivan Sutherland's Sketchpad (1963).  Douglas
   Engelbart's Augmentation of Human Intellect project at
   SRI in the 1960s developed the On-Line System, which
   incorporated a mouse-driven cursor and multiple windows.
   Several people from Engelbart's project went to Xerox PARC in
   the early 1970s, most importantly his senior engineer, Bill
   English.  The Xerox PARC team established the WIMP concept,
   which appeared commercially in the Xerox 8010 (Star) system
   in 1981.

   Beginning in 1980(?), led by Jef Raskin, the Macintosh
   team at Apple Computer (which included former members of the
   Xerox PARC group) continued to develop such ideas in the first
   commercially successful product to use a GUI, the Apple
   Macintosh, released in January 1984.  In 2001 Apple introduced
   Mac OS X.

   Microsoft modeled the first version of Windows, released
   in 1985, on Mac OS.  Windows was a GUI for MS-DOS that had
   been shipped with IBM PC and compatible computers since
   1981.  Apple sued Microsoft over infringement of the
   look-and-feel of the MacOS.  The court case ran for many
   years.

   [Wikipedia].

   (2002-03-25)