function enable_wpbakery_on_term_description() {
    if (class_exists('WPBakeryVisualComposerAbstract')) {
        add_filter('term_description', 'wpb_vc_enable_editor_on_term_description');
    }
}
add_action('init', 'enable_wpbakery_on_term_description');

function wpb_vc_enable_editor_on_term_description($content) {
    if (class_exists('WPBakeryVisualComposerAbstract')) {
        return do_shortcode($content);
    }
    return $content;
}