WordPress at a glance
action is not described

delete_post action-hook . WP 1.2.0

Fires immediately before a post is deleted from the database.

Usage

add_action( 'delete_post', 'action_function_name_4579', 10, 2 );
function action_function_name_4579( $postid, $post ){
	// action...
}
$postid(int)
Post ID.
$post(WP_Post)
Post object.

Changelog

Since 1.2.0 Introduced.
Since 5.5.0 Added the $post parameter.

Where the hook is called

wp_delete_post()
delete_post
wp_delete_attachment()
delete_post
wp-includes/post.php 3177
do_action( 'delete_post', $postid, $post );
wp-includes/post.php 6077
do_action( 'delete_post', $post_id, $post );

Where in WP core the hook is used WordPress

wp-includes/default-filters.php 410
add_action( 'delete_post', '_wp_delete_post_menu_item' );
wp-includes/default-filters.php 413
add_action( 'delete_post', '_wp_delete_customize_changeset_dependent_auto_drafts' );
wp-includes/default-filters.php 507
add_action( 'delete_post', 'delete_get_calendar_cache' );
wp-includes/ms-default-filters.php 79
add_action( 'delete_post', '_update_posts_count_on_delete' );
wp-includes/ms-default-filters.php 80
add_action( 'delete_post', '_update_blog_date_on_post_delete' );
wp-includes/nav-menu.php 1144
remove_action( 'delete_post', '_wp_delete_customize_changeset_dependent_auto_drafts' );
wp-includes/nav-menu.php 1156
add_action( 'delete_post', '_wp_delete_customize_changeset_dependent_auto_drafts' );