unregister_post_type( string $post_type )

function unregister_post_type( $post_type ) {
	global $wp_post_types;

	if ( ! post_type_exists( $post_type ) ) {
		return new WP_Error( 'invalid_post_type', __( 'Invalid post type.' ) );
	}

	$post_type_object = get_post_type_object( $post_type );

	// Do not allow unregistering internal post types.
	if ( $post_type_object->_builtin ) {
		return new WP_Error( 'invalid_post_type', __( 'Unregistering a built-in post type is not allowed' ) );
	}

	$post_type_object->remove_supports();
	$post_type_object->remove_rewrite_rules();
	$post_type_object->unregister_meta_boxes();
	$post_type_object->remove_hooks();
	$post_type_object->unregister_taxonomies();

	unset( $wp_post_types[ $post_type ] );

	/**
	 * Fires after a post type was unregistered.
	 *
	 * @since WP-4.5.0
	 *
	 * @param string $post_type Post type key.
	 */
	do_action( 'unregistered_post_type', $post_type );

	return true;
}