You can define symbols to represent commonly used
    class/instance pairs of NCL commands. Symbol definitions are
    provided to cut down on the amount of repetitive typing you must
    perform. Use the define and read control verbs to create and
    verify symbol definitions. For example:

     define      ncl symbol NAME = "VALUE"
     undefine    ncl symbol [ NAME | * ]
     show        ncl symbol [ NAME | * ]
     list        ncl symbol [ NAME | * ]

     ncl> define ncl sym rc1 = "routing circuit circuit-1"
     ncl> show rc1

     Node 0 Routing Circuit circuit-1
     AT 1994-07-14-15:10:10.976-04:00I0.226

     Identifiers

         Name               = circuit-1

     The first parameter to the define command is the symbol and
     all remaining text is the equivalence string (the translation
     of the symbol). The symbol can be from 1 to 500 characters in
     length and contain any ISO latin-1 characters (?). At definition
     time, the equivalence string is not parsed. NCL will parse the
     full NCL command and any symbols that form part of the command.

     To delete symbols, use the undefine verb. For example:

     ncl> undefine Ether,Remote_Node  ! To delete specific symbols
     .
     .
     .
     ncl> undefine *                  ! To delete all remaining symbols
     .
     .
     .

     You can use "." to mean "the entity used in the last command."