/sys$common/syshlp/helplib.hlb DELETE, /SYMBOL, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 symbol-name

    Specifies the name of the symbol to be deleted. A name is
    required unless the /ALL qualifier is specified. The symbol-name
    parameter is incompatible with the /ALL qualifier. Symbol names
    can have from 1 to 255 characters. By default, the DELETE/SYMBOL
    command assumes that the symbol is in the local symbol table for
    the current command procedure.