Source : Free On-Line Dictionary of Computing

chroot
     
         The {UNIX} command to make the {root
        directory} (/) become something other than its default for the
        lifetime of the current process.  It can only be run by
        privileged users and is used to give a process (commonly a
        network server such as {FTP} or {HTTP}) access to a restricted
        portion of the {file system}.
     
        The new root contains copies of all the essential files and
        directories, e.g. /lib, /dev/tty, /tmp.
     
        (1996-12-08)