WordPress at a glance
function is not described

register_term_meta() WP 4.9.8

Registers a meta key for terms.

No Hooks.

Return

true/false. True if the meta key was successfully registered, false if not.

Usage

register_term_meta( $taxonomy, $meta_key, $args );
$taxonomy(string) (required)
Taxonomy to register a meta key for. Pass an empty string to register the meta key across all existing taxonomies.
$meta_key(string) (required)
The meta key to register.
$args(array) (required)
Data used to describe the meta key when registered. See register_meta() for a list of supported arguments.

Code of register term meta: wp-includes/taxonomy.php VER 5.1.1

<?php
function register_term_meta( $taxonomy, $meta_key, array $args ) {
	$args['object_subtype'] = $taxonomy;

	return register_meta( 'term', $meta_key, $args );
}