WordPress at a glance
filter is not described

nav_menu_description filter-hook . WP 3.0.0

Filters a navigation menu item's description.

Usage

add_filter( 'nav_menu_description', 'filter_function_name_8350' );
function filter_function_name_8350( $description ){
	// filter...

	return $description;
}
$description(string)
The menu item description.

Where the hook is called

wp_setup_nav_menu_item()
WP_Customize_Nav_Menu_Item_Setting::value_as_wp_post_nav_menu_item()
wp-includes/nav-menu.php 845
$menu_item->description = apply_filters( 'nav_menu_description', wp_trim_words( $menu_item->post_content, 200 ) );
wp-includes/customize/class-wp-customize-nav-menu-item-setting.php 627
$post->description = apply_filters( 'nav_menu_description', wp_trim_words( $post->description, 200 ) );
wp-includes/nav-menu.php 873
$menu_item->description = apply_filters( 'nav_menu_description', '' );

Where the hook is used (in WP core)

Does not used.