WordPress at a glance
filter is not described

trackback_url filter-hook . WP 2.2.0

Filters the returned trackback URL.

Usage

add_filter( 'trackback_url', 'filter_function_name_3714' );
function filter_function_name_3714( $tb_url ){
	// filter...

	return $tb_url;
}
$tb_url(string)
The trackback URL.

Where the hook is called

get_trackback_url()
wp-includes/comment-template.php 1122
return apply_filters( 'trackback_url', $tb_url );

Where the hook is used (in WP core)

Does not used.