WordPress at a glance
action is not described

before_delete_post action-hook . WP 3.2.0

Fires before a post is deleted, at the start of wp_delete_post().

Usage

add_action( 'before_delete_post', 'action_function_name_2920', 10, 2 );
function action_function_name_2920( $postid, $post ){
	// action...
}
$postid(int)
Post ID.
$post(WP_Post)
Post object.

Changelog

Since 3.2.0 Introduced.
Since 5.5.0 Added the $post parameter.

Where the hook is called

wp_delete_post()
before_delete_post
wp-includes/post.php 3026
do_action( 'before_delete_post', $postid, $post );

Where in WP core the hook is used WordPress

wp-includes/post.php 488
add_action( 'before_delete_post', '_reset_front_page_settings_for_post' );