WordPress Version: .10
/**
* Registers a meta key for terms.
*
* @since 4.9.8
*
* @param string $taxonomy Taxonomy to register a meta key for. Pass an empty string
* to register the meta key across all existing taxonomies.
* @param string $meta_key The meta key to register.
* @param array $args Data used to describe the meta key when registered. See
* {@see register_meta()} for a list of supported arguments.
* @return bool True if the meta key was successfully registered, false if not.
*/
function register_term_meta($taxonomy, $meta_key, array $args)
{
$args['object_subtype'] = $taxonomy;
return register_meta('term', $meta_key, $args);
}