WordPress at a glance
action is not described

wp_register_sidebar_widget action-hook . WP 3.0.0

Fires once for each registered widget.

Usage

add_action( 'wp_register_sidebar_widget', 'action_function_name_5932' );
function action_function_name_5932( $widget ){
	// action...
}
$widget(array)
An array of default widget arguments.

Where the hook is called

wp_register_sidebar_widget()
wp_register_sidebar_widget
wp-includes/widgets.php 375
do_action( 'wp_register_sidebar_widget', $widget );

Where the hook is used (in WP core)

Does not used.