the primary display screen of a graphical user interface, on which various icons represent files, groups of files, programs, or the like, which can be moved, accessed, added to, put away, or thrown away in ways analogous to the handling of file folders, documents, notes, etc., on a real desk.
British Dictionary definitions for desktop computer
desktop
/ˈdɛskˌtɒp/
noun
1.
the main screen display on a personal computer, from which windows may be opened and programs run
2.
(modifier) denoting a computer system, esp for word processing, that is small enough to use at a desk
Word Origin and History for desktop computer
desktop
n.
1929, from desk + top. As an adjective meaning "suitable for use on a desktop," it is recorded from 1958 (in reference to computers). As a shortening of desktop computer, recorded from 1983. Desktop publishing recorded from 1984.