How to do a query on custom taxonomies that is uncategorised?

Question

Okay thanks for all the helpful comments. It turns out there is no way to do this using WP_QUERY alone.

The best way I can think of is to do it is like so:

$taxIds = get_terms($options['post-types'][$this->current_post_type->name], array(
                'fields'        => 'ids',
            ));
            $uncategorisedQuery = new WP_Query( array(
                'post_type'         =>  $postType,
                'posts_per_page'    => -1,
                'tax_query' => array (
                    array(
                        'taxonomy' => $taxonomyType,
                        'field' => 'term_id',
                        'terms' => $taxIds,
                        'operator' => 'NOT IN'
                    )
                )
            ) );

Although @shanbp had a nice idea of creating a “Uncategorised” taxonomy and automatically applying it to each post on creation if no taxonomy is selected.