Loop through each taxonomy term, run a new WP_Query in each term

taxonomy-query-loop.php

<?php

// Get terms
// http://codex.wordpress.org/Function_Reference/get_terms
// use $args array in second parameter if needed
$my_categories = get_terms( 'TERM_NAME_HERE' );
$my_categories_count = count( $my_categories );

if ( $my_categories_count > 0 && is_array( $my_categories ) ) {
	echo '<div class="wrap">';

	foreach ( $my_categories as $single_cat ) { ?>
		<h2><?php echo $single_cat->name; ?></h2>
		
		<?php
			$cat_posts_args = array(
				'post_type' => 'product',
				'order' => 'ASC',
				'orderby' => 'date',
				'post_status' => 'publish',
				'posts_per_page' => -1,
				'tax_query' => array(
					array(
						'taxonomy' => 'product_cat',
						'field' => 'id',
						'terms' => $single_cat->term_id,
						'include_children' => false
					)
				)
			);
			$cat_posts = new WP_Query( $cat_posts_args );

			if ( $cat_posts->have_posts() ) :

				echo '<p>';

				while ( $cat_posts->have_posts() ) : $cat_posts->the_post(); ?>

					<a href="<?php the_permalink(); ?>"><span><?php the_title(); ?></span>: <?php echo get_the_excerpt(); ?></a><br>

				<?php endwhile;

				echo '</p>';

			else :
				if ( !$parent ) echo '<p>No products found.</p>';
			endif;

			wp_reset_postdata();

		} // end foreach

	echo '</div>';
}

Thanks Matt Banks. I tested the tax_query args from this loop and they still work 5 years on.