From http://www.webdevdoor.com/wordpress/get-posts-custom-taxonomies-terms

query_posts_by_custom_taxonomy.php

<?php
$myposts = get_posts(array(
    'showposts' => -1,
    'post_type' => 'gallery',
    'tax_query' => array(
        array(
        'taxonomy' => 'gallery_cat',
        'field' => 'slug',
        'terms' => array('sunsets', 'nature'))
    ))
);
 
foreach ($myposts as $mypost) {
      echo $mypost->post_title . '<br/>';
      echo $mypost->post_content . '<br/>';
      echo  $mypost->ID . '<br/><br/>';
}
?>