You can use the term reference tree module, this gives you a taxonomy term theme function. Create a subtheme of seven and override the theme function in template.php. In the example below I am also using the tipsy module, which converts the .tipsy class into a tooltip, so the taxonomy term description appears after clicking or hovering on the tooltip on the node add form, but you could of course also just print the $description.
/** * This function prints a single item in the tree, followed by that item's children * (which may be another checkbox_tree_level). */ function seven_subtheme_checkbox_tree_item($variables) { $element = $variables['element']; $children = element_children($element); $output = ""; $sm = $element['#level_start_minimized'] ? ' term-reference-tree-collapsed' : ''; if (is_array($children) && count($children) > 1) { $output .= "<div class='term-reference-tree-button$sm'></div>"; } elseif (!$element['#leaves_only']) { $output .= "<div class='no-term-reference-tree-button'></div>"; } foreach ($children as $child) { // $child is the tid $term = taxonomy_term_load($child); $description = trim(strip_tags($term->description)); if (!empty($description)) { $tooltip = l('ⓘ', '#', array( 'attributes' => array( 'class' => array('tipsy'), 'title' => $description, ) )); } $output .= drupal_render($element[$child]) . $tooltip; } return $output; }