When this property is set to false, the menu item is disabled and no pop-out image indicating child items is displayed. Setting this property to false for a menu item essentially makes the menu item the end of that node, where no further levels are shown off of that node. The default value is true.

If you want the menu item to show any child items, but to not be "clickable" itself, use the MenuItem.Selectable property and set it to false.