The Collaborative International Dictionary of English v.0.48:

doorstop \door"stop`\, n. (Carp.)
   The block or strip of wood or similar material which stops,
   at the right place, the shutting of a door; any object used
   to stop open doors from moving.
   [1913 Webster]

WordNet (r) 3.0 (2006):

doorstop
    n 1: a stop that keeps open doors from moving [syn: doorstop,
         doorstopper]

The Free On-line Dictionary of Computing (19 January 2023):

doorstop

   Used to describe equipment that is non-functional and halfway
   expected to remain so, especially obsolete equipment kept
   around for political reasons or ostensibly as a backup.  "When
   we get another Wyse-50 in here, that ADM 3 will turn into a
   doorstop."

   Compare boat anchor.

   [Jargon File]


The Jargon File (version 4.4.7, 29 Dec 2003):

doorstop
 n.

    Used to describe equipment that is non-functional and halfway expected to
    remain so, especially obsolete equipment kept around for political reasons
    or ostensibly as a backup. Compare boat anchor.