<?php
/**
 * Exclude `Uncategorized` category from all terms lists.
 * @param  array $terms [description]
 * @return array        List of terms, less 1
 */
function xx_exclude_terms_uncategorized( $terms ) {
	$exclude_terms = [ 1 ]; // Exclude `Uncategorized` category
	if ( ! empty( $terms ) && is_array( $terms ) ) {
		foreach ( $terms as $key => $term ) {
			if ( in_array( $term->term_id, $exclude_terms ) ) {
				unset( $terms[$key] );
			}
		}
	}

	return $terms;
}
add_filter( 'get_the_terms', 'xx_exclude_terms_uncategorized' );