Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

doorstop
     n : a stop that keeps open doors from moving [syn: {doorstopper}]

Source : Free On-Line Dictionary of Computing

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}]