WordPress at a glance
action is not described

trash_post_comments action-hook . WP 2.9.0

Fires before comments are sent to the trash.

Usage

add_action( 'trash_post_comments', 'action_function_name_8883' );
function action_function_name_8883( $post_id ){
	// action...
}
$post_id(int)
Post ID.

Where the hook is called

wp_trash_post_comments()
wp-includes/post.php 2929
do_action( 'trash_post_comments', $post_id );

Where the hook is used (in WP core)

Does not used.