WordPress at a glance
action is not described

user_admin_notices action-hook . WP 3.1.0

Prints user admin screen notices.

Usage

add_action( 'user_admin_notices', 'action_function_name_2884' );
function action_function_name_2884(){
	// action...
}

Where the hook is called

In file: /wp-admin/admin-header.php
user_admin_notices
wp-admin/admin-header.php 257
do_action( 'user_admin_notices' );

Where the hook is used (in WP core)

wp-admin/includes/ms-admin-filters.php 14
add_action( 'user_admin_notices', 'new_user_email_admin_notice' );