WordPress at a glance
action is not described

delete_site_transient_(transient) action-hook . WP 3.0.0

Fires immediately before a specific site transient is deleted.

The dynamic portion of the hook name, $transient, refers to the transient name.

Usage

add_action( 'delete_site_transient_(transient)', 'action_function_name_8951' );
function action_function_name_8951( $transient ){
	// action...
}
$transient(string)
Transient name.

Where the hook is called

delete_site_transient()
wp-includes/option.php 1625
do_action( "delete_site_transient_{$transient}", $transient );

Where the hook is used (in WP core)

Does not used.