WordPress at a glance
action is not described

wp_update_nav_menu action-hook . WP 3.0.0

Fires after a navigation menu has been successfully updated.

Usage

add_action( 'wp_update_nav_menu', 'action_function_name_849', 10, 2 );
function action_function_name_849( $menu_id, $menu_data ){
	// action...
}
$menu_id(int)
ID of the updated menu.
$menu_data(array)
An array of menu data.

Where the hook is called

wp_update_nav_menu_object()
wp_nav_menu_update_menu_items()
wp-includes/nav-menu.php 381
do_action( 'wp_update_nav_menu', $menu_id, $menu_data );
wp-admin/includes/nav-menu.php 1083
do_action( 'wp_update_nav_menu', $nav_menu_selected_id );

Where the hook is used (in WP core)

Does not used.