WordPress at a glance
function is not described

unregister_block_type() WP 5.0.0

Unregisters a block type.

No Hooks.

Return

WP_Block_Type/false. The unregistered block type on success, or false on failure.

Usage

unregister_block_type( $name );
$name(string/WP_Block_Type) (required)
Block type name including namespace, or alternatively a complete WP_Block_Type instance.

Code of unregister block type: wp-includes/blocks.php WP 5.2.2

<?php
function unregister_block_type( $name ) {
	return WP_Block_Type_Registry::get_instance()->unregister( $name );
}