64:  How do I delete menus and menu options?

  The simplest way to remove a menu is to set its keymap to nil.  For
  example, to delete the "Words" menu (from question 63), use:

    (define-key global-map [menu-bar words] nil)

  Similarly, removing a menu option requires redefining a keymap entry to
  nil.  For example, to delete the "Forward word" menu option from the
  "Edit" menu (we added it in question 63), use:

    (define-key global-map [menu-bar edit forward] nil)