WordNet (r) 3.0 (2006):

desktop
    n 1: the top of a desk
    2: (computer science) the area of the screen in graphical user
       interfaces against which icons and windows appear [syn:
       background, desktop, screen background]

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

desktop

   1.  In a WIMP graphical user interface,
   the visual representation of a real desktop (the top surface
   of a piece of furniture) with documents, folders and a rubbish
   bin arranged on it.  The user manipulates files on the
   computer by using a mouse to click and drag their
   representations (icons) on the desktop.

   The WIMP interface and desktop metaphor was invented at Xerox
   PARC and popularised by the Apple Macintosh.

   2.  desktop computer.

   (2007-09-12)